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THE DIGESTIBILITY AND UTILIZATION 
OF EGG PROTEINS 



THE USE OF RAW EGGS IN 
PRACTICAL DIETETICS 



By 
W. G. BATEMAN 



From the Thesis Submitted for the Degree of Doctor of Philosophy 
Yale University, 1916 



rfip 



Reprinted from The Journal of Biological Chemistry, Vol. XXVI, No. 1, 1916 



THE DIGESTIBILITY AND UTILIZATION OF EGG 
PROTEINS. 

BY W. G. BATEMAN. 

(From the Sheffield Laboratory of Physiological Chemistry in Yale 
University, New Haven.) 

(Received for publication, June 24, 1916.) 

In 1898 Steinitz noted that the ingestion of raw egg-white by- 
dogs was followed by vomiting and diarrhea. This interesting 
observation appears to have passed almost unnoticed, although 
no other native proteins are known to give rise to such digestive 
disorders. When these same facts were observed by Mendel and 
Lewis in 1913, their possible bearing on the wide spread use of 
raw eggs in various diets, especially by the sick, prompted the 
following study. 

The Behavior of Egg-White in the Alimentary Tract. 
Experiments with Dogs. 

Native Egg-White. — Uncooked egg-white fed in any large quan- 
tity to dogs invariably caused diarrhea of more or less severity. 
The feces were soft, pasty, or liquid depending upon the amount 
of material ingested and upon the individual susceptibility of 
the subject. The more liquid stools were light in color, and of 
very offensive odor. Many of them contained much mucus, 
and residues of unchanged egg-white and of other foodstuffs. 
Upon standing the surface dried rapidly so as to assume a glazed 
or varnished appearance. Water extracts of the feces, when 
boiled, yielded varying amounts of coagulated protein material. 
The coagulation temperature varied from 68-73°. When an 
equal volume of saturated ammonium sulfate solution was added 
to the extract, the latter became turbid, but the grayish precip- 
itate contained only a trace of protein. The addition of acid or 
of more saturated ammonium sulfate solution to the filtrate caused 

263 



264 Utilization of Egg Proteins 

the formation of heavy precipitates which acted like ovalbumin. 
The substance, however, could not be obtained in crystals. The 
protein in the feces, then, appeared to be unchanged egg-white. 
The stools of firmer consistency contained less coagulable mate- 
rial than those which were liquid or semi-liquid. Even the ap- 
parently formed stools sometimes yielded small amounts of pro- 
tein upon extraction. In this connection Tsuchiya's (1909) 
statement that albumin is never found in real formed feces but 
is usually associated with diarrhea is pertinent. 

After eating meals containing enough raw egg-white to induce 
diarrhea, the subjects usually lost weight to the extent of from 
0.25 to 0.6 kilo, or from 3 to 8 per cent of the body weight. Some 
of the dogs remained stationary in weight, but none showed an 
increase in this respect. 

Vomiting only rarely occurred in consequence of ingesting 
native egg-white and then only after the larger amounts. The 
ejected material was practically unchanged by its stay in the 
stomach. 

In a few cases small intestinal hemorrhages were noticed, 
pointing to irritation of the intestinal mucosa. This occurred 
only after several days' feeding of the raw food or after much 
straining at stool. 

These abnormal conditions ceased promptly upon substitut- 
ing meat or "dog biscuit" for the egg-white and could be called 
forth again by the reverse. In no case was there any "hang- 
over" effect. Indeed the cessation of egg-white meals was usu- 
ally followed by constipation. The digestive disturbances which 
result from feeding dogs native egg-white are, therefore, caused 
directly by this substance. 

Urine, obtained by catheterization on those days when the ani- 
mals had diarrhea, usually gave negative results when tested for 
albumin; but occasionally small amounts were found present. 
These samples of urine also contained very little indican, due 
no doubt to the rapid emptying of the gut. 

Amount of Egg Necessary to Produce Diarrheal Symptoms. — 
The effects produced by the egg-white were roughly proportional 
to the amounts ingested. With dogs of 5.5 to 7 kilos in weight 
the white of one egg causes no or little effect, two eggs may cause 
softening of the feces, three cause marked softening, and four or 



W. G. Bateman 265 

five induce more or less severe diarrhea. The last symptom, then, 
is brought about by the ingestion of 1 to 1.5 gm. of native egg- 
white per kilo of body weight. This figure is lower for the heavier 
animals since dogs weighing from 10 to 12 kilos may develop 
diarrhea by eating the whites of five to seven eggs. There is 
much variation in the sensitiveness of the subjects, however; for 
a large dog may be more easily affected than a small one by the 
same amount of protein. 

Other Factors. — Diarrhea followed the ingestion of: (1) native 
egg-white unmixed with other foodstuffs; (2) native egg-white 
beaten with milk; (3) raw egg-white thoroughly mixed with 
cracker-meal and lard; (4) raw egg-white thoroughly mixed with 
cracker-meal and lard and well flavored with extract of beef. 
The first two types of meal produced the laxative effect more 
quickly than the other two, the stools being passed in 8 to 12 and 
12 to 20 hours respectively. The presence of a secretagogue 
such as meat extract in fairly large amount had no effect on the 
time of appearance or on the severity of the diarrhea. When a 
meal containing the whites of four or five eggs was divided into 
three portions which were fed to the dog several hours apart, the 
abnormal stool was later in appearing than when the meal was 
eaten all at the same time, and the diarrhea usually not so exten- 
sive. Conversely, if three of four egg-whites were fed at each 
meal several liquid stools were passed each day. 

Tolerance. — It was noticed that when the raw protein was fed 
for several days in succession its ill effects gradually waned. 
The time necessary for the abatement of the diarrheal action 
varied from 3 to 5 days. If then the ingestion were continued, 
there succeeded a period of alternate days of diarrhea and 
constipation after which time the egg ceased to exert any marked 
action. The tolerance thus developed lasted for a short time 
even after the feeding of the uncooked material was discontinued. 
These facts are brought out in the following typical protocol. 

Dog 1, a healthy terrier bitch weighing 6.52 kilos, received every day a 
meal containing the whites of four raw eggs well mixed with 60 gm. of 
cracker-meal and 20 gm. of lard. On the 1st day this caused severe diar- 
rhea with a fall in weight to 6.31 kilos. On the 2nd day the diarrhea con- 
tinued and the animal vomited some of the meal — one of the rare cases 
when this happened. The weight fell to 5.96 kilos. The stool on the 3rd 



266 Utilization of Egg Proteins 

day consisted of a smaller amount of semi-liquid feces. No further vomit- 
ing occurred but the weight fell to 6.9 kilos. On the 4th day the pasty 
feces were much smaller in bulk while the weight rose slightly. This 
improvement was followed on the 5th day by rather bad diarrhea but the 
weight was not changed and after this time there was no further loss in 
weight. The feces of the 6th day were small in amount and pasty. On 
the next 2 days no feces were passed. The 9th day's stool consisted of a 
large amount of fairly formed feces. On the 10th day no fecal matter was 
passed. The quantity of egg given was now increased to 'five whites but 
notwithstanding this the next 2 succeeding days showed well formed feces. 
On the 13th day the stool was small and somewhat pasty while it was well 
formed again on the next day. At this point the subject was put on a meat 
diet for 2 days. Then a meal containing the whites of five eggs failed to 
cause diarrhea. After 2 days more of meat diet, however, the whites of 
four eggs in the meal brought forth a liquid stool. In one subject this 
period of induced "immunity" lasted for 12 days. 

This tolerance recalls that acquired by the dogs subjected to 
peritoneal injections of raw egg-white as observed by Cramer 
(1908). He found that the protein was partly used and partly 
excreted in the urine. The quantity utilized rose gradually after 
repeated injections. Hamburger (1902) and Oppenheimer (1904) 
have observed this as well. That all proteins do not appear in 
the urine after injection intraperitoneally was shown by Mendel 
and Rockwood (1905) who found that edestin and excelsin were 
not excreted by the kidneys after introduction in this way. 

Utilization. — The finding of unchanged egg-white in the diar- 
rheal feces showed this foodstuff to be poorly utilized. The ex- 
tent to which it was used was roughly shown by extracting the 
24 hour feces with cold water, boiling this extract, and drying 
the coagulated material. The feces were made easier to handle 
by adding bone-ash to the meals and the feces of one period were 
marked off from those of another with lamp-black. After the 
ingestion of four to five egg-whites containing 15 to 19 gm. of 
protein, from 30 to 50 per cent of this could be recovered as coag- 
ulum. The latter, of course, contained varying amounts of oc- 
cluded substances. More exact estimates of utilization were 
furnished by determining the amount of nitrogen in the feces by 
the Kjeldahl method. This is open to the objection that a por- 
tion at least of the fecal nitrogen is not derived from the undi- 
gested foods but is contained in unadsorbed material of the in- 
testinal secretion and in epithelial cells from the intestinal tract. 



W. G. Bateman 



267 



According to Hammerl, Kermanner, Moeller, and Prausnitz (1897) 
and Tsuboi (1897) a large part of the nitrogen in the feces comes 
from these sources. Still another portion may be derived from 
the organisms living in the alimentary canal, for Osborne and 
Mendel (1914) have shown that a not inconsiderable part of the 
feces may consist of bacterial residues. But while the method 
does not show the exact amount of material digested, the figures 
so obtained do serve to show the relative degree of utilization. 
The following protocols are typical. 

TABLE I. 
Utilization of Raw Egg-While by Dog 1. 





Food. 


Nitrogen. 




Day. 


In food. 


In feces. 


Utilization. 


1 


Meat 


gm. 

2.50 
2.50 
2.50 
2.42 
2.42 
2.50 


gm. 

0.13 
0.12 
0.13 
1.22 
1.07 
0.17 


per cent 

94.7 


2 




95.2 


3 


a 


94.8 


4 
5 
6 


Raw egg-white 

u « a 

Meat 


49.8 
56.0 
93.1 



TABLE II. 
Utilization of Raw Egg-White by Dog 2. 





Food. 


Nitrogen. 




Day. 


In food. 


In feces. 




1-3 
4 
5 


Meat 

Raw egg-white 

« u a 


gm. 
9.04 
3.16 
3.18 


gm. 

0.33 
1.20 

1.28 


per cent 

96.3 
62.0 
59.5 



TABLE III. 
Utilization of Raw Egg-White by Dog 4- 





Food. 


Nitrogen. 


Utilization. 


Day. 


In food. 


In feces. 


1 

2 


Raw egg-white 

Meat 


gm. 
3.21 
3.05 


gm. 

1.06 

0.13 


per cent 

69.0 
95.8 



268 



Utilization of Egg Proteins 

TABLE IV. 
Utilization of Raw Egg-White by Dog 6. 





Food. 


Nitrogen. 




Day. 




Utilization. 






In food. 


In feces. 








gm. 


gm. 


pei- cent 


1 


Meat 


3.06 


0.11 


97.2 


2 


Raw egg-white 


2.97 


1.23 


58.6 



Native egg-white, then, was poorly made use of by these dogs, 
since from 30 to 50 per cent of the amount ingested was wasted 
by being ejected with the feces. When Mendel and Lewis (1913) 
fed this material to dogs only about half of the nitrogen in the 
meals appeared in the urine for the following 24 hours as con- 
trasted with almost all when meat, casein, edestin, and other pro- 
teins replaced the egg-white. Steinitz (1898) reported unchanged 
egg-white in the feces in considerable quantity but does not state 
the figures. Vogt (1906) and Falta (1906) found that the nitro- 
gen in uncooked egg-white superimposed upon a standard diet 
was excreted much more slowly in the urine than that ingested 
in the form of other proteins. The former ascribes this to a 
slower rate of digestion and the latter to the longer time neces- 
sary to catabolize the larger cleavage products which he supposes 
adsorbed. Both explanations are fundamentally the same — the 
native egg-white resists digestive processes. 

After the dogs had grown to tolerate the egg-white better, the 
utilization was better as well. For example, the feces passed by 
the subject described in the protocol under "tolerance" on the 9th 
and 12th days were analyzed for nitrogen with results shown in 
the following table. 





Improvement 


TABLE V. 

of Utilization with Tolerance. 




Day. 


Food. 


Nitrogen. 




In food. 


In feces. 


Utilization. 


9 
12 


Raw egg-white 

it u u 


gm. 
2.46 
3.15 


gm. 

0.39 
0.42 


per cent 

84.3 

86.7 



W. G. Bateman 



269 



Dried Egg-White. — The material was prepared by drying native 
egg-white in the air at temperatures below 50°. 15 to 20 gm. 
of the dry powder dissolved in water and fed in the usual meal of 
cracker-dust and lard were as active in causing diarrhea as the 
raw egg-white itself. This was also true with the subjects of 
Mendel and Lewis who consider the dried egg-white dissolved in 
water as equivalent to the original material. Neither was the 
utilization of the egg-white improved by drying. Several sam- 
ples were kept at a temperature of about 40° for periods varying 
from 3 to 7 days, but this again made little difference in their 
digestibility. Falta (1906) made experiments using desiccated 
material and found in three cases a utilization of 80 per cent, 80 
per cent, and 61 per cent respectively, while the same dogs used 
almost 100 per cent of casein and gelatin. The method used by 
Falta was that of superimposition. The feces were usually not 
analyzed but one dog was noted as having diarrhea. LeClerc 
and Cook (1906), in the course of work on another topic, fed to 
a dog meals containing dried albumin, cracker-dust, and lard 
together with sodium phosphate. They give the following- 
figures : 

TABLE VI. 
Nitrogen Balance on Diet Containing Egg-White (LeClerc and Cook). 



Experiment. 


Nitrogen. 


Utilization. 












In food. 


In urine. 


In feces. 


Balance. 






gm. 


gm. 


gm. 


gm. 


per cent 


1 


16.72 


9.55 


9.90 


-1.73 


40.8 


2 


16.71 


10.89 


6.18 


-0.37 


63.0 


3 


17.52 


6.62 


13.85 


-3.05 


21.0 



For the first and third experiments practically all the nitrogen 
was supplied in the form of egg-white, while for the second, half 
was in this form and half in egg-yolk. The differences in the 
balance and utilization are striking. On the last day it will be 
noted that the nitrogen in the feces was over twice that in the 
urine. These results may be compared with those given later 
in this paper. 

To determine what effect standing might have on the dried 
egg-white, experiments were made with commercial albumin 



270 Utilization of Egg Proteins 

which had been in the laboratory for some years. This caused 
diarrhea although not so severe as that induced by either the 
native or freshly dried protein. Its activity was not further 
diminished by being exposed to bright light for 2 months. The 
dogs showed considerable ability to overcome the effects of this 
substance. The following describes a typical case. 

Dog 4 was a healthy terrier bitch weighing 6.3 kilos. Its daily meal 
consisted of 60 gm. of cracker-dust, 20 gm. of lard, and 15 gm. of commer- 
cial egg-albumin dissolved in 150 cc. of water. On the 1st day severe 
diarrhea developed and the utilization of the protein was only 76 per cent. 
Next day the diarrhea was much less extensive but the weight of the sub- 
ject had fallen to 6 kilos. On the 3rd day no feces were passed but the quan- 
tity on the 4th day was large while the consistency was pasty. The utili- 
zation was now 82 per cent. On the 5th day there was only a small quan- 
tity of feces and this was true of the 7th day as well. On the alternate 
days — 6th and 8th — the feces were large in quantity and on the last named 
day better formed. The utilization had risen to 86.5 per cent. The native 
egg-white and the commercial product act, then, in much the same manner. 

In still other experiments the dried egg-white was fed without 
previous hydration or solution, only enough water being added 
to the meal to make it eatable. In these cases diarrhea did not 
generally occur. Water was left in the cages but no more was 
taken than usual. The quantity of urine was diminished and 
indican was usually present in notable amounts. The feces were 
delayed, sometimes not being passed until 23 to 25 hours after 
the meal. When finally passed they were soft, unformed, of 
strong odor, and contained much mucus. The utilization was 
better than in the previous experiments, since it was generally 
above 80 per cent. In a few cases, however, diarrhea did result 
from dried egg-white fed in this way. 

Cooked Egg-White. — When dogs ate the well cooked whites of 
four to six eggs they did not display the ill effects attending the 
use. of the same quantities of uncooked egg-white. Moreover, 
the cooked material was as effective in stopping the diarrhea 
caused by the raw eggs as was meat. The utilization was very 
good, being in the neighborhood of 90 per cent, as shown below. 
The marked difference in the metabolism of the same substance 
cooked on the one hand and raw on the other is brought out in 
the following tables. 



W. G. Bateman 



271 



TABLE VII. 

Nitrogen Balance of Dog 1. 





Meal. 


Nitrogen. 


Utilization. 


J 










Q 




In food. 


In urine. 


In feces. 


Balance. 








gm. 


gm. 


gm. 


gm. 


per cent 


1 


Cooked egg-white, 














cracker, lard 


3.76 


3.20 


0.33 


+0.23 


91.2 


2 


<< 


3.76 


2.91 


0.39 


+0.46 


89.6 


3 


Raw egg-white, 














cracker, lard 


3.81 


3.10 


1.87 


-1.16 


51.0 


4 


« 


3.74 


3.27 


1.31 


-0.84 


62.2 


5 


Cooked egg-white, 














cracker, lard 


3.76 


3.15 


0.43 


-0.18 


88.5 



TABLE VIII. 

Nitrogen Balance of Dog 5. 







Nitrogen. 


Utilization. 


• 


Meal. 










Q 




In food. 


In urine. 


In feces. 


Balance. 








gm. 


gm. 


gm. 


gm. 


per cent 


1 


Cooked egg-white, 














cracker, lard 


4.32 


3.95 


0.43 


-0.06 


90.0 


2 


Raw egg-white, 














cracker, lard 


4.36 


3.17 


1.81 


-0.72 


58.5 


3 


Cooked egg-white. . . 


4.32 


4.00 


0.44 


+0.12 


89.8 



It will be seen that the cooked egg-white was not so well util- 
ized as meat. For this two factors other than the nature of the 
foodstuff may be responsible. One is, that the dogs were fed 
generously which led as usual to more waste; and the other is 
the presence in the meal of bone-ash, for Mendel and Fine (1912) 
have demonstrated that even small amounts of indigestible sub- 
stances in the food cause a poorer use of protein. Kolpakcha 
(1888) found egg-white to be excellently utilized by dogs — 95 
per cent or better — even when large amounts were ingested. 
Although not specifically stated so, the material was probably 
cooked. Steinitz (1898), on the contrary, states that consider- 
able quantities of coagulated egg-white were passed in the feces 
of dogs. The differences may possibly be due to variations in 



272 Utilization of Egg Proteins 

the fineness of division since if dogs are allowed to bolt large 
pieces of hard-cooked egg-white, fragments of the same can gener- 
ally be distinguished macroscopically in the feces. 

The Temperature Necessary to Improve the Digestibility of Egg- 
White. — The above results show that simple heating of the native 
egg-white renders it more digestible and affords the organism a 
chance to make better use of it. At what temperature is this 
change effected? To determine this the egg-white was heated 
in a double-boiler for 30 to 45 minutes with constant stirring. 
At temperatures below 55° the substance suffered little impair- 
ment of its activity in causing diarrhea. This activity is, how- 
ever, considerably decreased by heating at 55° or 60°. After 
being subjected to a temperature of 65° for half an hour the 
digestibility of the egg-white is still further enhanced while at 
70° or above, the foodstuff becomes entirely innocuous. Above 
55°, more or less coagulation takes place depending upon the 
degree of alkalinity of the egg-white, while at 70° the protein is 
entirely coagulated but is very soft and jelly-like in texture. 

Experiments with Rats. 

The subjects were large, healthy, white rats kept in sanitary 
cages and supplied plentifully with food and water. The meals 
consisted largely of separator-milk powder ("Klim") mixed well 
with varying amounts of egg-white, bread-meal, and lard. 

When the diet contained 20 per cent of raw egg-white the feces 
of the subjects were not different from those of controls fed on a 
mixed diet although occasionally the presence of small amounts 
of coagulable protein could be demonstrated. When the pro- 
portion of egg-white was increased to 40 per cent half of the ani- 
mals had softened feces, the scybala being larger and longer than 
normal. Such stools as these always contained unused protein. 
All the subjects up to this time gained in weight and maintained 
excellent condition. Tolerance for the unusual foodstuff was 
quickly gained since after 7 to 10 days' feeding the feces could 
not be distinguished in appearance from those of the controls. 

Next, a new lot of animals were first fed a diet containing 60 
per cent of raw egg-white. This caused diarrhea which in some 
cases was severe. In the latter contingency the body weight 



W. G. Bateman 273 

decreased while the less susceptible animals, on the contrary, 
gained somewhat or remained stationary. The food was not 
relished so that the diminished intake played some part when 
weight was lost. The ill effects of the native egg-white were still 
more marked when the proportion in the food was increased to 
70 per cent. Several subjects refused to eat after a few days, 
moping in the cages and neglecting to clean themselves. The 
feces now became quite liquid at times and often contained 
mucus. When the fecal matter dried it appeared as though var- 
nished. In a final experiment the rats were fed a mixture of 80 
per cent raw egg-white and 20 per cent milk powder of which 
they partook rather sparingly. They lost weight rapidly, all 
were afflicted with diarrhea, and after 10 days it was evident that 
their health was much impaired. Six of these animals while 
having diarrhea were killed with chloroform and the intestines 
examined. In half the cases everything was normal while the 
degree of intestinal inflammation perceived in the other three did 
not appear significant. 

The use of cooked instead of raw egg-white was followed by no 
untoward effects. All the rats gained in weight and remained 
well and active even when the diet contained a large proportion 
of the coagulated protein. 

Falta and Noeggerath (1905) fed rats a diet in which dry egg-white was 
the only protein. The animals did not live longer than 94 days in the most 
favorable cases. The weight steadily declined and death followed when 
the weight fell to two-thirds or three-fifths of its original value. The rats 
suffered from conjunctivitis and other eye diseases. Knapp (1908) reports 
similar results. All his rats experienced diarrhea and conjunctivitis. 
One soon died, the others following in from 17 to 24 weeks, after losing 
much weight. Maignon (1912) fed rats exclusively on egg-white, either 
raw or cooked, which was found entirely inadequate to sustain them. 
Weight was quickly lost in spite of the increased quantities of food in- 
gested. Death occurred after various periods when the body weight had 
been much reduced — in some cases as much as 40 per cent. Frank and 
Schittenhelm (1912) also failed to nourish rats when the only protein 
furnished was egg-white. 

Von Knieriem (1885) fed mice exclusively on dry egg-white. They could 
not maintain existence and some succumbed in 3 days. Rohmann (1914) 
used mice as subjects, feeding them mixed diets some of which contained 
egg-white. He concluded from the results of his experiments that this 
substance sustained life poorly in comparison with other proteins. 

THE JOURNAL OP BIOLOGICAL CHEMISTRY, VOL. XXVI, NO. 1 



274 Utilization of Egg Proteins 

All the untoward effects noted by these investigators cannot be 
ascribed to the egg-white but more justly to the lack in the diet 
of important food accessories such as the vitamines. Osborne 
and Mendel (1911) kept rats growing well on rations containing 
cooked egg-white as sole protein for 170 days and the ensuing 
decline was arrested, not by changing the protein but by adding 
a small amount of butter fat. As regards the eye troubles, rats 
are prone to suffer from epidemics of conjunctivitis and other 
diseases if poorly nourished or kept in unsanitary surroundings. 
Both Falta and Noeggerath and Knapp experienced these troubles 
with other proteins in the diet than egg-white; but they appeared 
to be milder and more tractable in the former case. 

Experiments with Rabbits. 

The experimental animals were kept in metabolism cages and 
liberally supplied with mixed food. The raw egg-white was fed 
by means of a stomach sound. 

1. Two rabbits each received the whites of two eggs. One passed a 
small amount of semi-liquid matter while the feces of the other and of a 
control which received an equivalent quanity of water were normal. 

2. Two rabbits each were fed the whites of three eggs. One had mod- 
erate diarrhea while the feces of the other were pasty and increased in 
quantity above those passed on the mixed food. 

3. Three rabbits each were given the whites of two eggs at 10 o'clock 
and the whites of two more at 2 o'clock. Two were afflicted with diarrhea 
of some severity. One of them ate most of the fecal matter in preference 
to food. The third animal passed a large amount of very pasty feces, the 
scybala being much larger than normal. 

Von Knieriem (1885) fed three rabbits each a meal containing: 

gm. 

Dry egg-white 15 

Meat extract 5 

Sugar 10 

Horn shavings 2 

Water, cc 225 

The resulting feces were very soft and abnormal. Utilization 
of the egg-white in the three cases was calculated to be 61, 67.2, 
and 70.2 per cent respectively. The character of the feces and 
the poor utilization of the protein were doubtless due in part to 



W. G. Bateman 275 

the presence in the food of the horn shavings which acted in the 
same manner as the indigestible substances used in the experi- 
ments of Mendel and Fine and Mendel and Lewis. Neverthe- 
less, von Knieriem decided that egg-white was, in contrast to 
almost all other proteins, poorly digested. Mendel and Rose 
(1911) found it impossible to feed any large amount of native egg- 
white to rabbits without inducing diarrhea. 

Experiments on Man. 

Experiments were made with native egg-white and raw eggs 
upon a number of persons, and the cooperation of still others who 
were eating raw eggs in order to gain weight was secured. The 
data collected confirmed the points already brought out. Most 
of the subjects experienced diarrhea which generally abated after 
several days' ingestion of the raw foodstuff, and many complained 
of intestinal discomfort. The material was poorly utilized. 
These experiments will be discussed more in detail together with 
the question of the use of raw eggs in practical dietetics, in 
another place. 

The results of these experiments are in accord with those of 
other investigators. Falta (1906) found raw egg-white to be 
utilized by man to the extent of 70 per cent. A still lower value, 
50 per cent, was reported by Wolf (1912) who has described the 
peculiar behavior of this foodstuff when ingested by man. He 
did not observe diarrhea but the feces were of soft consistency. 
When raw egg-white was in the diet there was over twice as 
much nitrogen in the feces as when the food contained the same 
quantity of nitrogen in the form of other proteins. On one oc- 
casion the feces contained more nitrogen than did the urine. The 
latter did not contain albumin, a result in contrast to those of 
Hamburger (1902) and Cramer (1908) who claimed that albumi- 
nuria followed the ingestion of large doses of native egg-white by 
man. Previously Oertel (1883) had not been able to find albu- 
min in the urine in such cases, and neither did uncooked egg- 
white cause an increase in excreted albumin in preexisting albu- 
minuria. Wolf also noted that when either raw or cooked egg- 
white was superimposed upon a standard diet there was a delay 
in the excretion of nitrogen and sulfur, the delay being greater 



276 Utilization of Egg Proteins 

in the sulfur elimination. He suggested that the sulfur com- 
plexes in the uncoagulated egg-white have considerable power to 
withstand the action of the digestive enzymes. 

Explanations of the Behavior of Egg-White in the Alimentary Tract. 
The Effect of Heating on Egg-White. 

The improvement in the digestibility of raw egg-white effected 
by heating may be brought about by the increased temperature 
in four different ways. These are: (1) The temperature used 
in cooking kills any bacteria present; (2) heating changes the. 
physical texture of the egg-white; (3) heating destroys enzymes 
normally found in this native protein mixture; (4) heating 
changes the chemical nature of the egg-white. 

1. Heating Kills Bacteria. — That bacteria in the egg-white 
cause the diarrhea attending its use is improbable. It is true that 
Wiley (1908), Lamson (1909), Pennington (1910), Maurer (1911), 
and Stiles and Bates (1912) have reported a large percentage of 
the eggs examined by them infected. But the more recent work 
of Rettger (1913), who carried out far-reaching tests with the 
greatest care to prevent accidental contamination, led him to 
the opposite conclusion. Of the whites of 582 fresh eggs only 
seven, or 1.2 per cent, showed the presence of bacteria and some 
of these cases were unquestionably due to contamination. These 
results are supported by those of Horowitz (1902) and confirmed 
by Kossowicz (1913). And not only is egg-white usually sterile 
but it has strong antiseptic properties and in many cases a marked 
disinfectant action on bacteria as demonstrated by Lascht- 
schenko (1909) and Rettger and Sperry (1912). The bacteri- 
cidal properties are destroyed by heating the egg-white to 65-70°. 
In view of these facts it is unlikely that the unusual behavior of 
native egg-white in the alimentary tract can be due to bacteria. 

2. Heating Changes the Physical Texture. — When raw egg-white 
is heated above 55° it coagulates and loses its properties as a 
viscid liquid. It is possible that this change is responsible for 
the bettered digestibility of the cooked protein especially since, 
as shown above, this improvement is not brought about by heat- 
ing at temperatures too low to cause coagulation. 

Two sets of dogs were fed meals exactly alike except that one 



W. G. Bateman 277 

received native egg-white and the other cooked egg-white ground 
to a fine pulp. By the addition of water both types of meal were 
made as nearly of the same consistency as possible. Those 
meals containing the raw foodstuffs always caused diarrhea while 
the others did not. 

For further evidence on this point there was added to raw egg- 
white enough sodium hydroxide to prevent coagulation when the 
mixture was heated even above 70°. By this treatment the egg- 
white was little altered, only becoming somewhat more viscid; 
yet when fed to dogs it failed to cause diarrhea. 

Other experiments to be discussed later in detail also showed 
that the egg-protein could be made digestible without changing 
its fluid character. 

While it may be said that the peculiar physical nature of the 
substance is not per se the factor giving rise to diarrhea and poor 
utilization, the protein does, nevertheless, act while in the stom- 
ach in an unusual manner. Beaumont (1833) was the first to 
discover that raw egg-white leaves the stomach more rapidly 
than other foods, including cooked egg-white itself. Some ob- 
jections may be raised against these early observations because of 
the abnormality of Beaumont's subject; but that the protein does 
act in the manner described has been confirmed recently by Can- 
non (1905), and London and Sulima (1905). The former found 
the egg-white to pass through the pylorus at a rate comparable 
to that of the carbohydrates which are among the first foodstuffs 
to enter the intestine after ingestion whereas protein leaves the 
stomach slowly. The egg-white was the only protein to act in 
this way among those investigated. London and Sulima by 
means of intestinal fistulas found that the egg-white left the stom- 
ach in large gushes, often faster than the peristaltic waves. Dur- 
ing its stay in the stomach it retained its alkaline reaction for 
some time or passed into the intestine in this condition. After 
feeding a dog native egg-white these workers recovered 73 per 
cent unchanged from a fistula in the ileum. 

The amount of gastric proteolysis undergone by this protein, 
already decreased by its short stay in stomach, is still further 
diminished by another unusual property observed by Pawlow 
(1902); namely, that the egg-white acts ineffectively in stimu- 
lating a flow of gastric juice. It acts in this way only like 



278 Utilization of Egg Proteins 

so much water. But even this is not the end of the story, for 
Abderhalden and Pettibone (1912), and Bizarro (1913) state that 
native egg-white offers considerable resistance to the action of 
pepsin. If the egg-white is heated, however, and especially if 
coagulated at 80°, it is more quickly acted upon by the pepsin 
than when uncooked, and hydrolysis proceeds farther. After 
the material is once coagulated the rate of digestion is lessened 
by heating at higher temperatures. The fineness of division of 
the coagulum also affects the rate of digestion. 

We may picture this native protein, then, as quickly leaving 
the stomach, accompanied by scanty amounts of gastric juice 
and practically unaltered by pepsin. Perhaps this lack of gas- 
tric digestion is at the bottom of the egg-white's unusual behavior 
as a foodstuff. That it does have a bearing on the subject was 
shown by feeding dogs partially digested egg-white. The pro- 
tein together with 0.2 per cent pepsin and 0.2 per cent hydro- 
chloric acid was heated for several hours at 37°. The digestion 
was continued until the mixture upon neutralization gave a heavy 
precipitate, in the filtrates from which no coagulable protein 
could be detected. This material, which was little altered in 
texture from the original, was as inactive as cooked egg-white in 
causing diarrhea. 

However, Cannon, and London and Sulima have shown that 
even coagulated egg-white leaves the stomach much more rapidly 
than other proteins, although less so than when in the native con- 
dition. When cooked it does, in contrast to the raw material, 
call forth an early secretion of hydrochloric acid with which it 
unites. But the difference in rate of gastric discharge is not 
enough to account for the differences in digestibility, so one must 
consider the behavior of the two in the intestine. 

As stated above, the native egg-white in the stomach fails to 
cause a good flow of gastric juice. According to the mechanism 
which Bayliss and Starling (1902) propose for the action of secre- 
tin, it is probable that once in the intestine the raw egg-white 
meets comparatively little pancreatic juice since the amount of 
the latter is proportional to the quantity of acid entering the 
duodenum — a fact observed by Pawlow (1902) as well. Fur- 
thermore, Bruno and Klodnizki (1914) showed that no bile was 
passed into the intestine when raw egg-white was ingested. 



W. G. Bateman 279 

Okada (1915) has confirmed this to the extent that in his experi- 
ments the secretion of bile was small and seemed to be dependent 
upon the degree of digestion undergone by the protein in the 
stomach. Coagulated egg-white always caused a good flow of 
bile. 

3. Heating Destroys Enzymes. — In the intestine the digestion 
of the egg-white is still further checked by the pronounced re- 
sistance it exerts against the action of trypsin. Vernon (1904) 
found the antitryptic activity to be more marked with this pro- 
tein than with any other. In solutions containing 0.5 to 1.0 per 
cent of raw egg-white the trypsin action on fibrin was lowered 
to only 2.7 per cent of the normal, while even one part of egg- 
white in 6,000 reduced the activity to 45 per cent of the normal. 
When the egg albumin was exposed to a temperature of 60° its 
antitryptic influence was not diminished and it retained a good 
deal of its inhibitory power even after coagulation at 100°. 

The native egg-white, however, is unlike collagen which is not 
acted upon at all by trypsin; for Bayliss (1908) has shown that 
if sufficient time be allowed the enzyme will act as completely 
upon uncooked as upon cooked egg albumin. For some hours 
after being brought together the trypsin does not change the egg- 
white in the slightest degree and it requires over 70 hours before 
the digestion equals that of the cooked material under the same 
conditions. Hedin (1907), Cohnheim (1912), Abderhalden and 
Pettibone (1912), Long and Johnson (1913), and Bizarro (1913) 
have all demonstrated the strong antitryptic effect of egg-white 
which Hammarsten (1912) considers remarkable. 

To explain this behavior the existence of a specific anti-enzyme, 
antitrypsin, has been postulated which is supposed to unite with 
the trypsin much as an antitoxin does with its corresponding 
toxin. A later view is that the trypsin is adsorbed by the colloi- 
dal egg-white which thus cuts down tryptic activity in much the 
same way as did charcoal in the experiments conducted by Hedin 
(1906, b). Recently Maxwell (1915) has shown that boiled 
starch adsorbs pepsin and so hinders its activity. That egg- 
white does act in this manner is suggested by the observations of 
Delezenne and Pozerski (1903), Vernon (1904), Gompel and 
Henri (1905), and Hedin (1907) who found that raw egg-white 
prevents the tryptic digestion of other easily digested proteins. 



280 Utilization of Egg Proteins 

It has already been stated that native egg-white resists peptic 
digestion. It is interesting to note that proteolytic enzymes 
other than those occurring in the intestinal tract are also unable 
to act upon this substance. The work of Chittenden, Joslin, and 
Meara (1892), and Chittenden (1894) showed that raw egg-white 
was much more poorly digested than coagulated egg-white by 
bromelin, the proteolytic enzyme of the pineapple. Jonescu 
(1907) and Sachs (1907) found that papain was practically un- 
able to act upon native egg-white. If the latter was heated or 
incubated with dilute acids the antiproteolytic action toward 
papain was destroyed. 

If native egg-white contains antitrypsin, then heating may 
improve its digestibility by destroying the anti-enzyme. Tala- 
rico (1910) found that preliminary heating of the egg-white aided 
tryptic digestion. There was no effect, however, until the tem- 
perature reached 70° after which there was an orderly liberation 
of amino-acids up to 130°. Frank (1911) also found cooked egg- 
white to be better digested than raw, the optimum temperature 
being 70-75°. At temperatures above this the digestibility de- 
creased in proportion to the hardness of the coagulated material. 
Bizarro (1913) considered the best temperature to be 80°. In 
addition to these observers Abderhalden and Pettibone (1912) 
and Long and Johnson (1913) found the coagulated egg-white 
much better digested than the raw. The latter observers state 
that cooked egg-white, however, is acted upon slowly by trypsin 
as compared to pepsin. 

It is significant that the temperature (70°) which was found 
sufficient to rob the egg-white entirely of its activity in causing 
•diarrhea is the same as that given above for the optimum activity 
of trypsin. 

Beyond the resistance to trypsin the properties of the alleged 
antitrypsin in the egg-white are little known except that Vernon 
(1904) found its action much weakened by heating with dilute 
sodium carbonate. Hedin (1904) also used sodium carbonate to 
destroy the anti-enzyme. 

The following experiments were made to determine whether 
the antitrypsin could be the source of the unusual behavior of 
egg-white. 

The whites of five to six eggs were dialyzed for several days. 



W. G. Bateman 281 

When fed to dogs this material was effective in causing diarrhea. 
The antitrypsin, if present, is not diffusible. Cathcart (1904) 
found that the antitryptic action of blood serum is not removed 
by dialysis. 

Egg-white was incubated with 0.2 per cent sodium or potassium hydrox- 
ide or 0.25 per cent sodium or potassium carbonate for several hours at 
37°. Fed to dogs the material was no different in behavior than cooked 
egg-white. This treatment does not alter the texture to any extent. 

The native protein was heated in an incubator at 37° for 4 to 8 hours 
with 0.2 per cent acetic or hydrochloric acid. By this treatment it was 
rendered digestible and no diarrhea followed its use. This process also 
left the original texture unaltered. 

Jobling and Petersen (1915) succeeded in extracting antitryp- 
sin from blood serum with chloroform. It was found impracti- 
cable to extract native egg-white with chloroform or ether since 
a considerable quantity of the protein was precipitated and the 
liquids, especially the chloroform, did not separate well. After 
standing for 12 to 24 hours the mixtures were dried rapidly in 
a current of warm air at room temperature. The dry material 
was thoroughly mixed with water and fed to dogs. It did not 
cause diarrhea. Nothing had been removed from the native egg- 
white and judging by the work of Jobling and Petersen the 
treatment was scarcely drastic enough to destroy the anti-enzyme. 

Further attempts at extraction were made more successfully 
by previously drying and powdering the egg-white. In order to 
make the extraction as complete as possible the mixture of dry 
egg-white and ether or chloroform was allowed to stand for 4 
days, on each of which it was well shaken for a period of 30 to 60 
minutes. The extract was then separated and evaporated to 
dryness at room temperature. The residue from the extract was 
triturated with water and mixed as well as possible with finely 
minced, coagulated egg-white. This mixture, assumed to con- 
tain any antitrypsin originally in the egg-white, failed to cause 
diarrhea when fed to dogs. The residues insoluble in chloroform 
or ether were dried, mixed with water, and fed to dogs with nega- 
tive results. 

It is well known that enzymes in general are soluble in dilute and 
precipitated by strong alcohol. Egg-white was coagulated with 
strong alcohol and filtered. If antitrypsin was precipitated by 



282 Utilization of Egg Proteins 

the reagent it should be contained in the coagulated protein; yet 
when this was freed from alcohol and fed to dogs it caused no 
diarrhea. Neither did the filtrate appear to contain antitrypsin, 
for the residue obtained from it by evaporation well mixed with 
cooked egg-white was fed to dogs with no untoward results. In 
still other experiments the egg-white was precipitated as before 
with strong alcohol. After filtering, the coagulated protein was 
finely minced, ground up with dilute alcohol, and finally washed 
with dilute alcohol. By this treatment it might be supposed 
that antitrypsin, if present in the egg-white, would first be pre- 
cipitated and then washed out of the finely divided coagulum 
by the dilute alcohol. Accordingly the filtrates and washings 
were evaporated until the alcohol was removed and fed to dogs 
after being thoroughly incorporated with cooked egg-white. In 
no case was diarrhea induced. Finally the washed coagulum was 
fed but proved as ineffective as the extracts. 

Those of the above experiments, therefore, which were planned 
to remove an active substance from egg-white — by extraction or 
washing — appeared to fail since the separated material did not 
render cooked egg-white indigestible. In contrast, those experi- 
ments calculated to make the native egg-white digestible by de- 
stroying the anti-enzyme were successful. It may justly be 
argued, however, that antitrypsin, even if contained in the resi- 
dues from the extracts, cannot be mixed intimately enough with 
cooked egg-white to make it really indigestible. 

4- Heating Changes the Chemical Nature. — When egg-white is 
coagulated its chemical nature is altered. This change may be 
the causal factor in bettering its behavior in the intestinal canal. 
Changes of like nature brought about by other agents than heat 
were similarly effective. 

Some of the experiments already described bring out this point. 
Thus egg-white precipitated with alcohol did not affect dogs as did 
the original protein. It made no difference whether the precipi- 
tate was filtered off at once or allowed to stand in contact with the 
alcohol for several days. In other experiments the egg-white 
was denatured by the minimum quantity of moderately strong 
alcohol and the whole mixture dried quickly at a low temperature. 
This material sometimes considerably softened the feces of dogs 
by which it was ingested but this may be due to the fact that the 
treatment usually leaves some of the original protein unaltered. 



W. G. Bateman 283 

It has already been stated that dried egg-white extracted with 
chloroform or ether was readily digested. When these residues, 
from which little had been removed by extraction, were mixed 
with water and fed to dogs they did not cause diarrhea. Some- 
times, after the extraction had been made with ether, the feces 
were softer than normal. This lack of activity was not because 
the reagents extracted any active material as shown above, but 
apparently because the protein was more or less denatured by 
them. Before extraction the dried egg-white was entirely solu- 
ble in water, but the treatment so changed it that much of it 
became insoluble. 

Egg-white was chemically modified in still another way by 
converting it into alkali-metaprotein. This was prepared by 
the gradual addition of potassium hydroxide to native egg-white 
with constant stirring. The transparent jelly was finely divided 
and thoroughly washed with cold water. Fed to dogs it proved 
an excellent foodstuff. The feces formed by it closely resembled 
the normal feces in being dry and crumbly. Klug (1897) found 
that pepsin from the stomach of dogs digested alkali-albumin 
better than any other protein in his list, at the bottom of which 
he placed coagulated egg-white. In general the same thing was 
true with pig and ox pepsin. Vernon (1904) considered alkali- 
albumin prepared from egg-white more easily digested by trypsin 
than the native protein. 

As stated previously, if egg-white is partially predigested by 
pepsin or incubated with dilute acids and bases it loses its ability 
to cause diarrhea. All of these procedures, in addition to any 
effect they may have on antitrypsin, change the chemical 
nature of the egg-white. It is true that some of these changes 
are not pronounced, but in this respect the altered substances 
may be like the racemized proteins of Dakin and Dudley (1913) 
who found that such a slight chemical change as a partial reversal 
of the direction of polarization was sufficient to convert casein 
into an entirely indigestible substance. 

Resume. — From the evidence at hand it is reasonable to assume 
that the indigestibility of the egg-white is due primarily neither 
to its physical texture nor to any bacteria present. But it seems 
impossible to make a decision between the other two explana- 
tions offered, the difficulty being that any process affecting one 



284 Utilization of Egg Proteins 

factor modifies the other as well. Thus, when incubation with 
acid improves the digestibility of the native protein, we may 
explain it from the one view-point as due to the destruction of 
the antitrypsin, and from the other as due to the conversion of 
the indigestible egg-white into digestible acid-metaprotein. When 
treatment with chloroform renders the egg-white digestible, we 
may assume that this is caused either by the removal or, destruc- 
tion of the anti-enzyme, or by the change effected in the chemi- 
cal properties of the protein. 

The simplest assumption is that raw egg-white is attacked 
with much difficulty by the digestive enzymes. It is not con- 
tended that raw starch, agar, collagen, cellulose, and other in- 
digestible substances contain anti-enzymes. Moreover, the 
existence of such substances has been seriously doubted of late 
by investigators like Bayliss (1908) and Cohnheim (1912), the 
latter of whom considers that, "the evidence does not permit us 
to speak of specific antiferments." Probably the explanation of 
the behavior of antitryptic substances most in favor at present, is 
that which postulates an adsorption of the trypsin, the effective 
concentration of which is thereby reduced. 

What Component of Egg-White Is Responsible for Its Peculiar 
Behavior in the Alimentary Tract. 

The Action of the Individual Proteins of Egg-White. 

The proteins of egg-white were separated from each other 
according to the method of Osborne and Campbell (1900). Care 
was taken to have the various fractions as free from each other 
as possible and each was dialyzed free from ammonium sulfate 
before being used. The amounts of the various proteins used 
were equivalent to those contained in the whites of five or six 
eggs, which amount of egg-white had previously been found 
sufficient to cause severe diarrhea in the dogs used as subjects. 

Globulin. — According to Osborne and Campbell globulin is 
present in egg-white to the extent of 7 per cent of the total solids. 
The whites of five or six eggs contain approximately 1.5 to 2 gm. 
of globulin. These amounts of freshly prepared, moist globu- 
lin mixed with the usual meal did not affect the dogs in the least 
and the same was true when quantities four or five times as 



W. G. Bateman 285 

large were ingested. Even 20 gm. of purified egg globulin pre- 
pared 2 years previously did not perceptibly alter the consistency 
of the feces, although it was not very well utilized. 

Ovalbumin. — -The ovalbumin was obtained in fine cyrstals. 
After being dialyzed it was quickly dried at a low temperature. 
Osborne and Campbell succeeded in crystallizing 50 per cent of 
the total proteins in egg-white but consider that all the other 
fractions contain more or less of this substance. While the actual 
proportion present is, then, somewhat doubtful, for these experi- 
ments it was assumed to be 60 per cent. The whites of five or 
six eggs would then contain 12.5 to 16 gm. of ovalbumin. Fed 
in these amounts to dogs it caused diarrhea which was more 
marked when larger amounts were ingested. Its action, how- 
ever, was not so marked as might be expected from the activity 
of the native egg-white itself and was also more variable. Thus 
one dog, for instance, in which diarrhea had been induced several 
times with raw egg-white failed to react at all to the ovalbumin. 
Perhaps this is not surprising considering the amount of manipu- 
lation necessary to obtain the pure ovalbumin. While the glob- 
ulin is separating the mixture becomes strongly alkaline from the 
formation of ammonium hydroxide, and another change — pos- 
sibly oxidative — is going on as shown by the gradually deepening 
color of the solution. Later the ovalbumin stands for a long time 
in contact with acid, is dialyzed for several days, and dried. 
Osborne and Campbell indeed regard the crystallized substance 
as different from the original protein and consider that it is prob- 
ably a combination of the protein with acid. 

Conalbumin. — The amount of uncrystallizable albumin in egg- 
white is not definitely known but it is probably from 25 to 35 per 
cent of the total proteins. In five or six egg-whites there would 
be 4.5 to 6 gm. of conalbumin. Fed in these amounts it generally 
caused the formation of pasty feces, which effect was increased 
where the amount ingested was larger. A mixture of ovalbumin 
and conalbumin in the proportion in which they occur in egg- 
white fed to dogs in amounts equivalent to" 85 per cent of the total 
proteins in five or six egg-whites caused diarrhea. 

Ovomucoid. — It seems unlikely that ovomucoid is the disturb- 
ing protein of the egg-white since it is present in small amount — 
10 per cent according to Hammarsten, — is unaffected by heating 



286 Utilization of Egg Proteins 

in boiling water, and is precipitated unchanged by alcohol, so 
that it was present in the alcohol precipitates which failed to 
cause diarrhea. This supposition was confirmed by feeding to 
dogs ovomucoid prepared as follows. The whites of five or six 
eggs were diluted with water and the globulin and albumins 
coagulated by boiling after the addition of a little acetic acid. 
The filtrate containing the ovomucoid was fed to dogs mixed 
with the usual meal but did not cause diarrhea. 

The albumin fraction, therefore, appears to be the indigestible 
portion of the egg-white. This is in harmony with the observa- 
tions of Mendel and Lewis who found that purified ovalbumin 
fed to dogs in comparatively large amounts caused profuse diar- 
rhea. Vernon (1904) found crystallized albumin to be even more 
resistant to trypsin than native egg-white. Bainbridge (1911) 
noted that certain forms of bacteria do not appreciably break 
down this substance even in the presence of sufficient non-nitro- 
genous food to insure vigorous bacterial growth. In view of 
these results it is interesting that the antitryptic action of blood- 
serum according to Hedin (1904), Cathcart (1904), and Vernon 
(1908) is associated with the albumin and not with the globulin. 

The Digestibility of Duck Egg-White. 

Experiments with the white of the eggs of the Eastern Indian 
Runner demonstrated that it, too, was indigestible, caused diar- 
rhea, and was poorly utilized. The egg-white of the common 
fowl, then, is not unique in its exceptional conduct as a foodstuff. 
The egg of the duck appears to have been little investigated but 
the white differs in appearance from that of the hen's egg, and 
Panormow (1906) thought that it contained a special protein not 
found in other eggs. 

The Behavior of Egg-Yolk in the Alimentary Tract. 

When egg-yolk was fed to dogs in any large quantity as part 
of a meal containing lard and cracker-dust, it usually caused a 
rather severe digestive disturbance of which vomiting was the 
main symptom. The vomitus contained much bile, and fre- 
quently comparatively large amounts of this liquid were ex- 
pelled from the stomach. Diarrhea sometimes accompanied this 



W. G. Bateman 287 

vomiting. The subjects were apathetic and had little appetite 
for several days. These effects were brought about by cooked 
as well as by raw egg-yolk. The picture of this digestive dis- 
order is thus quite different from that induced by native egg-white. 

The regurgitation of bile suggested the fat as the cause of the 
trouble. Therefore the lard was omitted from the meal with 
favorable results since no diarrhea or vomiting was then noted. 
The same end was attained by extracting the fat from the egg- 
yolk by means of ether. The crude yolk-protein, freed from ether, 
was fed with lard and cracker-meal to dogs, and was inactive. 
The dogs affected by egg-yolk in the way described seem, then, 
to have had a low tolerance for fat. The disturbing effect of the 
yolk is considerably less than that of the white; for while, in one 
case, the whites of four raw eggs caused diarrhea the same sub- 
ject ate six raw yolks with impunity. 

The egg-yolk and ovovitellin were found to be excellently utilized 
and there appears to be nothing in the literature to show that 
they are indigestible. Mendel and Lewis' (1913) experiments 
showed the excretion of nitrogen after feeding ovovitellin to be 
the same as that after meat, a result in opposition to that obtained 
with coagulated and uncoagulated egg-white where the nitrogen 
excretion was delayed. McCollum (1909) sustained life in white 
rats for 18 weeks on nothing but egg-yolk with no unfavorable 
results, while it may be recalled that Maignon, Knapp, and von 
Knieriem could not keep dogs, rats, or mice alive on egg-white 
alone. Laschtschenko (1909) found that bacteria thrived well 
on egg-yolk, that it does not possess germicidal properties, and 
cuts down the bactericidal action of the egg-white.,. 

SUMMARY. 

Raw egg-white is found to be a decidedly indigestible substance. 
It may cause diarrhea in dogs, rats, rabbits, and man when in- 
gested in any large quantity. Its utilization by the body is poor 
since it is used only to the extent of 50 to 70 per cent. Subjects 
can acquire a certain tolerance for the native protein after ingest- 
ing it for several days so that it no longer causes diarrhea and is 
somewhat better utilized. 

Raw egg-white can be made digestible through coagulation 



288 Utilization of Egg Proteins 

by heat; by precipitation with alcohol, chloroform, or ether; by 
incubation with dilute acids or alkalies; by partial digestion by 
pepsin; by conversion into alkali-metaprotein. 

The indigestibility of native egg-white probably lies either in 
its antitryptic content or in its chemical constitution. Its physi- 
cal texture appears to play a minor part in its behavior. 

Of the individual proteins constituting egg-white, the albumin 
fraction appears to be the indigestible component. 

The whites of the hen's egg and duck's egg act alike in causing 
diarrhea and in being poorly utilized. 

Egg-yolk either raw or cooked is excellently utilized. It some- 
times causes digestive disturbances in dogs, apparently because 
of its high fat content. 

A review of the literature shows that dietitians have relied, 
in general, upon the early observations of Beaumont as support 
for the use of raw eggs: These observations were in the main 
exact; but, so far as the digestibility of raw egg-white is concerned, 
were misinterpreted. 

In current dieto-therapy raw whole eggs, raw egg-white, and 
albumin-water are extensively prescribed. There appears to be 
little in their conduct as foodstuffs, however, to warrant such 
faith in their nutritive value or ease of assimilation. 

In conclusion it is a pleasure to thank Dr. Lafayette B. Mendel 
for his kindness and helpfulness during the course of this work. 

REFERENCES. 

Abderhalden, E., and Pettibone, C. J. V., Uber den Einfluss des physi- 
kalischen Zustandes von Proteinen auf die Raschheit ihres Abbaues 
durch Fermente, Z. physiol. Chem., 1912, lxxxi, 458. 

Atwater, W. O., and Langworthy, C. F., A digest of metabolism experi- 
ments, U. S. Dept. Agric, Office of Exp. Stations, Bull. 4-5, 1898. 

Bainbridge, F. A., The action of certain bacteria on proteins, J. Hyg., 
1911, xi, 341. 

Bayliss, W. M., The Nature of Enzyme Action, London, 1908. 

Bayliss, W. M., and Starling, E. H., The mechanism of pancreatic secre- 
tion, J. Physiol., 1902, xxviii, 325. 

Beaumont, W., Experiments and Observations on the Gastric Juice, and 
the Physiology of Digestion, Plattsburg, 1833. 

Bizarro, A. H., On the influence of preliminary heating upon peptic and 
tryptic proteolysis, J. Physiol., 1913, xlvi, 267. 



W. G. Bateman 289 

Bruno, G. G., and Klodnizki (quoted from: Babkin, B. P., Die aussere 

Secretion der Verdauungdrusen, Berlin, 1914). 
Cannon, W. B., The passage of different food-stuffs from the stomach 

and through the small intestine, Am. J. Physiol., 1905, xii, 387. 
Cathcart, E. P., On the antitryptic action of normal serum, J. Physiol., 

1904, xxxi, 497. 
Chittenden, R. H., Joslin, E. P., and Meara, F..S., On the ferments con- 
tained in the juice of the pineapple, Tr. Connecticut Acad. Arts and 

Sc, 1892, viii, 281. 
Chittenden, R. H., On the proteolytic action of bromelin, the ferment of 

pineapple juice, J. Physiol., 1894, xv, 249. 
Cohnheim, O., Enzymes, New York, 1912. 
Cramer, W., On the assimilation of protein introduced parenterally, J. 

Phijsiol., 1908, xxxvii, 146. 
Dakin, H. D., and Dudley, H. W., The action of enzymes on racemized 

proteins and their fate in the animal body, J. Biol. Chem., 1913, 

xv, 271. 
Delezenne, C, and Pozerski, E., Action empechante de "l'ovalbumine 

crue" sur la digestion tryptique de "l'ovalbumine coagulee," Compt. 

rend. Soc. biol., 1903, lv, 935. 
Falta, W., Studieren iiber den Eiweissstoffwechsel, Deulsch. Arch. klin. 

Med., 1906, lxxxvi, 517. 
Falta, W., and Noeggerath, C. T., Futterungsversuche mit kunstlicher 

Nahrung, Beitr. chem. Phys. u. Path., 1905, vii, 313. 
Frank, P., The digestibility of white of egg as influenced by the temper- 
ature at which it is coagulated, J. Biol. Chem., 1911, ix, 463. 
Frank, F., and Schittenhelm, A., IJber die Brauchbarkeit tief abgebauter 

Eiweissprr.parate fur die Ernahrung, Therap. Monat., 1912, xxvi, 112. 
Gompel, M., and Henri, V., Etude du ralentissement que produit l'albu- 

mine d'oeuf crue sur la digestion tryptique de l'albumine coagulee, 

Compt. rend. Soc. biol., 1905, lviii, 457. 
Hamburger, F., Zur Frage der Immunisierung gegen Eiweiss, Wien. klin. 

Woch., 1902, xv, 1188. 
Hammarsten, O., A Textbook of Physiological Chemistry, New York, 6th 

edition, 1912. 
Hammed, H., Kermanner, F., Moeller, J., and Prausnitz, W., Untersuch- 

ungen uber das Verhalten animalischer und vegetabilischer Nahrungs- 

mittel im Verdauungskanal, Z. Biol., 1897, xxxv, 287. 
Hedin, S. G., Investigations on the proteolytic enzymes of the spleen of 

the ox, J. Physiol., 1904, xxx, 155. 
Hedin, On the antitryptic action of serum albumin, J. Physiol., 1905, a, 

xxxii, 390. 
Hedin, Action of trypsin, J. Physiol., 1905, b, xxxii, 468. 
Hedin, Trypsin and antitrypsin, Biochem. J., 1906, a, i, 474. 
Hedin, An antitryptic effect of charcoal, Biochem. J., 1906, b, i, 484. 
Hedin, Tiber verschiedenartige Hemmung der tryptischen Verdauung, Z. 

phijsiol. Chem., 1907, lii, 412. 



290 Utilization of Egg Proteins 

Horowitz, Contribution a l'etude des moyens de defense de l'organisme 

contre l'invasion microbienne, These de Paris, 1902, abstr. in Jahresber. 

path. Mikroorgan., 1903, xix, 984. 
Jobling, J. W., and Petersen, W. F., A study of the ferments and antifer- 

1 ments of the body, Bull. Johns Hopkins Hosp., 1915, xxvi, 356. 
Jonescu, D., Uber eine eigenartige Verdauung des Hijhner- und Serum- 

eiweiss durch Papain, Biochem. Z., 1907, ii, 177. 
Klug, F., Beitrage zur Pepsinverdauung, Arch. ges. Physiol., 1897, lxv, 

330. 
Knapp, P., Experimenteller Beitrag zur Ernahrung von Ratten mit 

ktinstlicher Nahrung, Z. exp. Path. u. Therap., 1908-09, v, 147. 
Kolpakcha (quoted from Atwater and Langworthy), Phiziol. Sbornik, 

Charkoff, 1888, i, 56. 
Kossowicz, A., Die Zersetzung und Haltbarmachung der Eier, Wiesbaden, 

1913. 
Lamson, G. H., Infection and preservation of eggs, Storrs Agric. Exp. 

Station, Bull. 55, 1909. 
Laschtschenko, P., Uber die keimtotende und entwicklungshemmende 

Wirkung von Hiihnereiweiss, Z. Hyg., 1909, lxiv, 419. 
LeClerc, J. A., and Cook, F. C, Metabolism experiments with organic 

and inorganic phosphorus, J . Biol. Chem., 1906-07, ii, 203. 
London, E. S., and Sulima, A. T., Zum Chemismus der Verdauung im tier- 

ischen Korper, Z. physiol. Chem., 1905, xlvi, 209. 
Long, J. H., and Johnson, W. A.., Activity and stability of certain fer- 
ments. II, J. Am. Chem. Soc, 1913, xxxv, 1188. 
Maignon, F., Role des graisses dans l'utilisation de Palbumine alimentaire, 

Compt. rend. Soc. biol., 1912, lxxii, 1054. 
Mauer, The bacteriology of eggs and egg products, Kansas State Agric. 

Coll., Exp. Station Bull. 180, 1911. 
Maxwell, The relation of salivary to gastric digestion, Biochem. J., 1915, 

ix, 323. 
McCollum, E. V., Nuclein synthesis in the animal body, Am. J. Physiol., 

1909-10, xxv, 127. 
Mendel, L. B., and Fine, M. S., The utilization of proteins, J. Biol. Chem., 

1912, xi, 5. 
Mendel, L. B., and Lewis, R. C, Rate of elimination of nitrogen as in- 
fluenced by diet factors, J. Biol. Chem., 1913-14, xvi, 55. 
Mendel, L. B., and Rockwood, E. W., On the absorption and utilization 

of proteins, Am. J . Physiol., 1905, xii, 336. 
Mendel, L. B., and Rose, W. C, Experimental studies on creatine and 

creatinine, J. Biol. Chem., 1911-12, x, 213. 
Oertel, M. J., Ueber Ernahrung mit Huhnereiern, Munich, 1883. 
Okada, S., On the secretion of bile, J. Physiol., 1914-15, xlix, 458. 
Oppenheimer, C, Uber das Schicksal der mit Umgehung des Darmkanals 

eignefuhrten Eiweissstoffe im Tierkorper, Beitr. chem. Phys. u. Path., 

1904, iv, 263. 
Osborne, T. B., and Campbell, G. F., The protein constituents of egg- 
white, /. Am. Chem. Soc, 1900, xxii, 422. 



W. G. Bateman 291 

Osborne, T. B., and Mendel, L. B., Feeding experiments with isolated 

food-substances, Carnegie Institution of Washington, Publication No. 

156, 1911. 
Osborne and Mendel, The contribution of bacteria to the feces, J . Biol. 

Chem., 1914, xviii, 177. 
Panormow, A. A., Uber einige Eigenschaften der Albumine im Eiweiss der 

Enteneier, Biochem. Centr., 1906, v, 171. 
Pawlow, LP., The Work of the Digestive Glands, London, 1902. 
Pennington, M. E., A chemical and bacteriological study of fresh eggs, 

./. Biol. Chem., 1909-10, vii, 109. 
Rettger, L. F., The bacteriology of the hen's egg, with special reference to 

its freedom from microbic invasion, Centr. Bakteriol.,2 teAbt., 1913-14, 

xxxix, 611. 
Rettger, L. F., and Sperry, J. A., The antiseptic and bactericidal proper- 
ties of egg-white, /. Med. Research, 1912, xxvi, 55. 
Rohmann, F., Uber die Ernahrung von Mausen mit einer aus einfachen 

Nahrungsstoffen zusammengesetzten Nahrung, Biochem. Z., 1914.. 

lxiv, 30. 
Sachs, F., Uber die Verdauung von rohem Hiihnereiweiss durch Papain, 

Z. physiol. Chem., 1907, li, 488. 
Steinitz, F., Ueber das Vernal ten phosphorhaltiger Eiweisskorper im Stoff- 

wechsel, Arch. ges. Physiol., 1898, lxxii, 75. 
Stiles, G. W., and Bates, C, A bacteriological study of shell, frozen, and 

desiccated eggs, U. S. Dept. Agric, Bureau of Chem., Bull. 158, 1912. 
Talarico, J., De 1' influence de la cuisson sur la digestibilite tryptique de 

l'albumine d'oeuf, Compt. rend. Soc. biol., 1910, lxviii, 662. 
Tsuboi, J., Ueber die Stickstoffausscheidung aus dem Darm, Z.Biol., 1897, 

xxxv, 68. 
Tsuchiya, I., Ueber das Auftreten des gelosten Eiweisses in den Faces 

Erwachsener, Z. exp. Path. u. Therap., 1909, v, 455. 
Vernon, H. M., The protective value of proteids and their decomposition 

products on trypsin, J. Physiol., 1904, xxxi, 346. 
Vernon, Intracellular Enzymes, London, 1908. 
Vogt, H., Der zeitliche Ablauf der Eiweisszersetzung bei verschiedener 

Nahrung, Beitr. chem. Phys. u. Path., 1906, viii, 409. 
Von Knieriem, W., Ueber die Verwerthung des Cellulose im thierischen 

Organismus, Z. Biol., 1885, xxi, 67. 
Wiley, H. W., A preliminary study of the effects of cold storage on eggs, 

quail, and chickens, U. S. Dept. Agric, Bureau of Chem., Bull. 115, 

1908. 
Wolf, C. G. L., Die Ausschiedungszeit von Stickstoff, Schwefel, und 

Kohlenstoff nach Aufnahme von Eiweisssubstanzen und ihren Spal- 

tungsprodukten. II, Biochem. Z., 1912, xl, 234. 



Extracted from the American Journal of the Medical Sciences, 
June, 1917, No. 6, vol. cliii, p. 841. 



THE USE OF RAW EGGS IN PRACTICAL DIETETICS. 
By W. G. Bateman, Ph.D., 

MISSOULA, MONTANA. 

(From the Sheffield Laboratory of Physiological Chemistry in Yale University, 
New Haven, Conn.) 



During the past fifteen years evidence has been gradually 
accumulating which shows that raw egg-white occupies an excep- 
tional position among native protein foodstuffs. Pawlow (1902) 
observed that this substance has only a feeble ability to stimulate 
a flow of gastric juice. It acted in this way only as so much water. 
Cooked egg-white, on the contrary, calls forth an abundance of 
juice and unites easily with the hydrochloric acid. On account 
of the scanty supply of secretion which it induces the raw protein 
has little opportunity to be digested, but this slender chance is 
still further diminished by another unusual property. Beaumont 
(1833), during his famous experiments on Alexis St. Martin, was 
the first to note that native egg-white left the stomach very rapidly 
in comparison to other foods, including cooked egg-white itself. 
Indeed, this substance spent a shorter time in the stomach than 
any other Beaumont investigated. This observation has more 
recently been confirmed by Cannon (1904) and by London and 
Sulima (1905). The former found that the egg-white passed 
through the pylorus at a rate comparable to that of the carbo- 
hydrates, which are among the first foodstuffs to enter the intestine 
after ingestion. Proteins leave the stomach slowly and egg-white 
was the only exception noted among those investigated. London 
and Sulima found that this hasty exit from the stomach was 
most striking. A few moments after ingestion the egg-white 
escaped in large gushes through a pyloric fistula. During its 
stay in the stomach it retains its alkaline reaction and passes into 
the intestine, for the most part entirely unchanged. After feeding 
a dog native egg-white these workers recovered large amounts 
unchanged from a fistula as far down the canal as the ileum. 

But even this does not exhaust the means by which raw egg- 
white escapes gastric digestion, for Abderhalden and Pettibone 
(1912) and Bizarro (1913) discovered that it offers considerable 



2 bateman: use of raw eggs in practical dietetics 

resistance to the action of pepsin. If, however, the egg-white 
is coagulated it is more readily acted upon by the pepsin, and 
proteolysis proceeds further. 

We may picture this native protein then as quickly leaving 
the stomach, accompanied by scanty amounts of gastric juice 
and little altered by pepsin. This peculiar behavior is consistently 
carried on in the intestine. Bruno and Klodnizki (1914) and 
Okada (1915) showed that little or no bile was passed into the 
intestine after the ingestion of raw egg-white, whereas the same 
material cooked always caused a good flow of bile. 

Once in the intestine the native egg-white continues to oppose 
the digestive enzymes, for it has remarkably strong antitryptic 
properties. The trouble is not that trypsin is unable to act upon 
the protein but that the rate of action is so slow. Bayliss (190S) 
found that it required seventy hours for the digestion of the raw 
material to equal that of the cooked, all other conditions being the 
same in the two cases. Indeed, the trypsin appears not to change 
the egg-white at all. Vernon (1904) found the antitryptic action 
to be more marked with this protein than with any other. Hedin 
(1907), Cohnheim (1912), Abderhalden and Pettibone (1912), Long 
and Johnson (1913), and Bizarro (1913) have all demonstrated 
the strong antitryptic action of egg-white. Not only does it 
resist digestion itself, but it prevents the digestion of other easily 
digested proteins, as observed by Delezenne and Pozerski (1903), 
Vernon (1904), Compel and Henri (1905), and Hedin (1907). 
This suggests that the true cause of both facts is that the colloidal 
egg-white absorbs the trypsin, thus cutting down its activity in 
much the same way as the charcoal in the experiments of Hedin 
(1906 b). Recently it has been shown by Maxwell (1915) that 
boiled starch absorbs pepsin and so hinders its activity. 

In view of both its antipeptic and antitryptic action it is inter- 
esting to note that other proteolytic enzymes are also unable to 
successfully cope with this native protein. Chittenden, Joslin 
and Meara (1892), and Chittenden (1894) showed that raw egg- 
white was much more poorly digested than coagulated egg-white 
by bromelin, the proteolytic enzyme present in the pineapple. 
Jonescu (1907) and Sachs (1907) found that papain was also 
practically unable to act upon native egg-white. 

Preliminary heating of the egg-white greatly increases its 
digestibility by trypsin. Talarico (1910) found that there was 
no effect, however, until the temperature reached 70°, after which 
there was an orderly liberation of amino-acids up to 130°. Frank 
(1911) also found cooked egg-white to be better digested than 
raw, the optimum temperature in his experience being 70° to 75°. 
Bizarro (1913) considered the best temperature for this prelimi- 
nary heating to be 80°. Abderhalden and Pettibone (1912) and 
Long and Johnson (1913) made similar observations. 



bateman: use of raw eggs in practical dietetics 3 

This brief review of its properties shows that native egg-white 
offers such obstacles to digestion as to place it in an exceptional 
position among the proteins. This raises the question as to how 
the body handles such a substance. Very little upon this point 
has, up to the present, been recorded, although raw eggs and egg- 
white have enjoyed a great vogue as the mainstay of various 
diets, especially for the sick. Steinitz (1898) noted incidentally 
that raw egg-white caused vomiting and diarrhea in dogs, but 
this interesting observation remained unnoticed. When the 
same facts were observed again by Mendel and Lewis (1913) they 
led to an extended study by the author, carried out during the 
past year, the details of which have been published elsewhere. 
This showed native egg-white to be a decidedly indigestible sub- 
substance. When fed to dogs in any considerable quantitv it 
invariably caused diarrhea and sometimes induced vomiting. 
The severity of the diarrhea depended largely upon the amount 
of material ingested, but also, to a less extent, upon the individual 
susceptibility of the subject. With dogs of 5.5 to 7 kilos in weight 
four or five egg-whites were sufficient to cause more or less severe 
diarrhea. Even the whites of two eggs often caused softening of 
the feces. The stools were abnormal in character, very offensive 
in odor, and often contained much mucus. After the ingestion 
of even small amounts of native egg-white the latter could be 
recovered unchanged in small quantity from the stools, and when 
the amount ingested was large the proportion of coagulable protein 
in the feces was correspondingly increased. 

Even when the feces appeared normal undigested egg-white 
could usually be recovered. In this connection, Tsuchiya's (1908) 
statement that albumin is never found in normal feces is pertinent. 

After eating enough egg-white to give rise to diarrhea the dogs 
usually lost weight. In a few cases small intestinal hemorrhages 
were observed. Occasionally samples of urine obtained by cathe- 
terization were found to contain small amounts of protein. In 
all these reactions there was found much variation in the sen- 
sitiveness of the subjects, for sometimes a large dog was more 
easily affected than a small one by the same amount of protein. 

It made little difference with the action of the egg-white 
whether it was eaten alone or mixed with other food. In the 
latter case the diarrhea was later in appearing. The presence 
in the food of a substance able to cause a good flow of gastric 
juice — meat extract for example — had no effect upon the time of 
appearance or severity of the diarrhea. 

It was soon noticed that when the raw protein was fed for 
several days in succession its ill effects gradually waned. The 
time necessary for the abatement of the diarrheal action varied 
from three to five days. If now the ingestion were continued 
there ensued a period of alternate days of diarrhea and constipa- 



4 bateman: use of raw eggs in practical dietetics 

tion, after which the egg-white ceased to exert any marked action. 
The tolerance thus developed lasted for a short time even after 
the feeding of the uncooked material was discontinued. This 
recalls the tolerance acquired by dogs who receive peritoneal 
injections of raw egg-white. Cramer (1908), Hamburger (1908), 
and Oppenheimer (1904) have observed that under such condi- 
tions the dogs utilized part of the protein and excreted the rest 
in the urine. After repeated injections the quantity used rose 
gradually. It might be supposed that all proteins would appear, 
at least in part, in the urine after injection intraperitoneally, but 
Mendel and Lockwood (1904) have shown this not to be the case 
with edestin and excelsin. 

Native egg-white was found poorly utilized. In large doses 
from 30 to 50 per cent, of that ingested was wasted by being 
ejected with the feces. After the dogs had grown to tolerate this 
material it was better utilized, but even in these cases the best 
figure was about 85 per cent. When Mendel and Lewis (1913) 
fed this substance to dogs only about half of the nitrogen in the 
meals appeared in the urine for the following twenty-four hours 
as contrasted with almost all when meat, casein, and other pro- 
teins were fed instead of the egg-white. Steinitz (1898) reported 
unchanged egg-white in the feces in considerable quantities. Vogt 
(1906) and Falta (1906) found that the nitrogen in uncooked 
egg-white superimposed upon a standard diet was excreted in the 
urine much more slowly than that ingested in the form of other 
proteins. 

Drying the egg-white at low temperatures did not abate its 
diarrheal activity nor improve its utilization. Neither did long 
standing. Falta (1906) also made experiments, using desiccated 
material, and found in three cases a utilization of SO per cent., 
80 per cent., and 61 per cent, respectively. LeClerc and Cook 
(1906) found the same substance very poorly utilized. 

"When dogs ate cooked egg-white in place of the native or desic- 
cated protein they did not have diarrhea and the material was 
excellently utilized, the utilization being in the neighborhood of 
90 per cent. When raw and cooked egg-white were fed on alter- 
nate days or periods the differences in the utilization and in the 
nitrogen balance were striking. 

Experiments were made to show at what temperature the change 
in digestibility became effective. By heating for thirty to forty- 
five minutes in a double boiler with constant stirring the egg-white 
suffered little impairment of its activity in causing diarrhea up to 
55°. Above this the activity is considerably decreased and dis- 
appears entirely at 70°. It should be noted that above 55° coagu- 
lation begins and at 70° the protein is entirely coagulated, but is 
very soft and jelly-like in texture. 

In order to show that dogs did not have an exceptional inability 



bateman: use of raw eggs in practical dietetics 5 

to digest native egg-white, experiments similar to the above were 
made, using rats and rabbits as subjects. These had in both cases 
the same results. Both rats and rabbits had diarrhea with con- 
sequent poor utilization of the protein. The hardy rats, however, 
were less sensitive than the other animals. That this native pro- 
tein sustains life in rats poorly in comparison to others is the 
general conclusion drawn from the work of Falta and Noeg- 
gerath (1906), Knapp (1908), Maignon (1912), and Frank and 
Schittenhelm (1912). Von Knieriem (1885) and Rohmann (1914) 
reached the same decision from work with mice as subjects. 
Osborne and Mendel (1911), on the contrary, kept rats growing 
well on rations containing cooked egg-white as sole protein for 
as long as one hundred and seventy days. Von Knieriem (1885) 
found that desiccated egg-white caused rabbits to pass very soft 
and abnormal feces containing much unchanged egg-white. 
Mendel and Rose (1911) found it impossible to feed any large 
quantity of raw egg-white to rabbits without inducing diarrhea. 

No other native proteins are known to act in the alimentary 
tract in the manner brought out by these experiments. On 
account of the importance of the subject from the stand-point 
of dietetics it was of interest to determine how raw egg-white 
comported itself when ingested by man. The experiments 
described below lead to the same conclusions already formulated. 

The first group of subjects included a number of men and women 
partaking of a diet consisting largely of raw eggs and milk for the 
purpose of increasing weight. 

Case I. — Subject O. B. This was a man, aged twenty-five 
years, who took two to three raw eggs beaten up in milk three 
times a day. During the first three days there was rather severe 
diarrhea and general malaise and after that regular stools of soft 
consistency. The subject had previously been somewhat con- 
stipated. 

Case II. — Subject D. S. was a man, aged forty years, who also 
took two raw eggs beaten up in milk three times a day. He did 
not experience diarrhea, but did have regular stools sometimes 
twice a day, whereas before beginning the diet he had had some- 
what obstinate constipation. He drank a large quantity of milk 
which generally would tend to prevent diarrhea. 

Case III. — Subject M. R., a woman, aged twenty-five years, 
ate six to eight raw eggs per day. The first few days there was 
extensive diarrhea followed for some time by irregular movements, 
consisting usually of soft material. 

Case IV. — Subject INI. H., a young woman, aged twenty-two 
years, who ate two raw eggs at night and the same number in the 
morning. There was no decided diarrhea, but previous consti- 
pation was overcome and the stools were soft. This subject 
complained of some intestinal discomfort. 



6 bateman: use of raw eggs in practical dietetics 

Case V. — Subject D. G., a woman, aged thirty-five years, took 
two or three raw eggs in milk three times a day. In this ease 
there was diarrhea for two days, although not severe. This was 
followed by a day without a stool, after which the bowels moved 
regularly every day. There had been no previous constipation. 

Case VI. — A man, aged about thirty-five years, took each night 
before retiring two raw eggs in whisky. On almost every such 
occasion he suffered much intestinal discomfort, accompanied with 
colic-like pains. Considering raw eggs to be "bland" and the 
whisky beneficial he did not discontinue the treatment for some time. 

Another group of subjects ate only the whites of raw eggs 
experimentally. 

Case I. — Subject D. S., a young woman, aged eighteen years, 
was unaffected by eating the whites of two eggs per day. When 
the number was doubled, diarrhea ensued accompanied by dis- 
comfort and some trouble with intestinal gases. 

Case II. — Subject B. B., aged thirty years, remained unaffected 
by eating every morning the whites of two to four eggs. She did 
notice discomfort and accumulation of gas. When the number 
was increased to six per day the subject complained of malaise and 
took an aversion to the diet. There was flatulence but no diarrhea. 

Case III. — Subject A. B., a child, aged three years. One-half 
of a raw egg-white ingested each day led to such laxness that the 
experiment was discontinued after the third day. The diarrhea, 
then, disappeared at once. 

Case IV. — Subject J. B., aged five years, was, on the contrary, 
quite unaffected by the same amount of egg-white as was given 
the last subject. 

Case V. — Subject W. B., a man, aged thirty years, was found 
quite unsusceptible to the native egg-white, since two to six whites 
failed to cause any noticeable change in the feces. When half a 
dozen eggs were eaten at once he experienced decided discomfort, 
associated with flatulence. An analysis of the stool for nitrogen 
showed the protein ingested to be only 85 per cent, utilized. Even 
eight to nine raw whites eaten at one time did no more than soften 
the feces, but the utilization was still poorer than before, being only 
77 per cent. At no time was there any protein in the urine. 

Case VI. — Subject L. M., aged twenty-five years, ate the whites 
of six raw eggs every third day. On each occasion the stool was 
soft and unformed. 

Falta (1906) found this material to be utilized by man to the 
extent of 70 per cent. Wolf (1912) reported a still lower value, 
namely, 50 per cent. In the latter case the feces were of soft 
consistency although no diarrhea was observed. There was over 
twice as much nitrogen in the feces when the raw egg was in the 
diet as when the food contained the same amount of nitrogen 
in the form of other proteins. On one day there was more nitro- 



bateman: use of raw eggs in practical DIETETICS i 

gen in the feces than in the urine. The latter did not contain 
albumin. 

Hamburger (1902) and Cramer (1908) claim that albuminuria 
follows the ingestion of large doses of native egg-white by man. 
Oertel (1883) had not been able to find albumin in the urine of 
either dogs or men after the ingestion of large quantities or raw or 
half-cooked egg-white. Neither did this material cause an increase 
in excreted albumin in preexisting albuminuria. Another aspect 
of this debated problem will be considered later. 

It is a matter of common experience that cooked egg-white has 
not been known to cause any exceptional digestive effects, and is 
well utilized. Rubner (1879), who seems to be the sole investi- 
gator to have fed a subject on cooked eggs only, found the utili- 
zation to be 97 per cent. Cathcart and Green (1913) found a 
delay in the excretion of nitrogen after superimposition of both 
native and coagulated egg-white, but the delay appears greater 
in the sulphur than in the nitrogen elimination. These authors 
and Wolf (1912), who noticed the same facts, believe that the 
sulphur complexes in the uncoagulated egg-white have power to 
withstand the digestive enzymes. 

Raw egg-white can be made digestible by other means than 
heating at 70°. This result can be brought about by incubation 
with dilute acids and alkalies at 37°; by precipitation with alcohol, 
chloroform, or ether; by partial digestion with pepsin, and by 
conversion into alkali metaprotein. 

Egg-white is not a homogeneous substance, but consists of at 
least four components — ovoglobulin, ovalbumin, conalbumin, and 
ovomucoid. These were separated according to the method of 
Osborne and Campbell (1900). When fed to dogs the albumin 
fraction proved to be the indigestible constituent, a result in 
harmony with the observations of Mendel and Lewis, who found 
that purified ovalbumin caused profuse diarrhea when fed to 
dogs. Vernon (1904) states that crystallized albumin is even 
more resistant to trypsin than native egg-white. 

All the experiments so far described were made with egg-white 
from the egg of the common fowl. That it is not unique in its 
unusual behavior in the alimentary tract was shown when the 
egg-white from the egg of the duck was found to act in exactly 
the same manner. 

In contrast to egg-white, egg-yolk was found to be well digested 
and utilized. There appears to be nothing in the literature to 
suggest that the latter is indigestible. Mendel and Lewis's (1913) 
experiments showed the excretion of nitrogen after feeding ovo- 
vitellin to be the same as that after meat, a result in opposition to 
that obtained with both coagulated and uncooked egg-white. In 
the author's experiments the feeding of egg-yolk either cooked or 
raw in any quantity of dogs usually caused a rather severe digestive 



8 bateman: use of raw eggs in practical dietetics 

disturbance, of which vomiting was the main symptom. The 
vomitus contained much bile and sometimes this liquid was alone 
expelled from the stomach. This suggested that the high fat 
content of the yolk was the cause of the trouble. This assump- 
tion was correct, for when the fat was extracted the residue of 
crude ovovitellin was eaten by dogs with no untoward effects. 

These experiments show, then, that raw egg-white is a decidedly 
indigestible substance. It may cause diarrhea and vomiting when 
ingested in any large quantity. Its utilization by the body is 
poor, since it is used only to the extent of from 50 to 70 per cent. 
What bearing have these facts upon practical dietetics? 

It is difficult to say to what extent raw eggs are ordinarily used. 
Since there is a wide-spread idea that they are especially digestible 
and very nutritious, one might expect their use to be common. 
There is no doubt that this is so when the diet in disease is con- 
sidered, for raw eggs appear to play an important part in systems 
of dietetics for the sick. It is likely that Beaumont's (1833) 
observations gave the first impetus to this dieto-therapeutic move- 
ment. According to his views digestion takes place in the stomach 
and absorption in the intestines. The criterion of digestibility 
was the time a food remained in the stomach, the assumption 
being that it passed the pylorus only when properly prepared 
by digestion for ensuing absorption through the intestinal mucosa. 
Since native egg-white left the stomach more rapidly than any 
other food the conclusion seemed obvious that it is a very readily 
digested substance. Beaumont says: 

"Albumin if taken into the stomach either very slightly or not at 
all coagulated is perhaps as readily chymified as any article of diet 
we possess. If coagulated it experiences a very protracted diges- 
tion. In the first case the albumin becomes finely coagulated and 
divided in the stomach." 

While the fact that raw egg-white does remain in the stomach 
only a short time is true, the interpretation of the fact was erro- 
neous. These experiments of Beaumont, the first of their kind, 
attracted much attention and became widely known. The earlier 
writers on dietetics based their advice in many details upon his 
work. Chambers in his Manual of Diet (1875), after quoting a 
table of Beaumont's showing the times spent in the stomach by 
raw eggs and eggs cooked in various ways, says, 

"It may be observed that this is just the order in which they 
are tasty — that is to say, the degree in which they come with facility 
into contact with the sensory nerves distributed through the 
mucous membrane — so that duty and pleasure here, as usually in 
natural operations, become one." 

To such a school nature is always right; it would not be thought 
possible for her to be so mistaken as to allow albumin to leave the 
stomach practically undigested. 



bateman: use of raw eggs in practical dietetics 9 

Although these early views on digestion are no longer supported 
by such arguments they still appear to be accepted almost un- 
questioned. In 1906 a Farmers' Bulletin of the United States 
Department of Agriculture quotes Beaumont's work and helps to 
spread the impression that raw eggs are very easily digested, since 
they are "chymified" in one and a half to two hours as against 
three for soft-boiled eggs. The figures for "artificial digestion," 
which approximated bodily conditions as closely as possible, are 
even more impressive, since it appears that it requires eight hours 
for the digestion of hard-boiled eggs, six hours for soft-boiled eggs, 
and only four hours for raw eggs. This bulletin, which has been 
extensively circulated, gives also the results of experiments which 
show that cooked eggs are thoroughly digested. Still more recently 
in Practical Dietetics for Nurses, Pattee (1910) quotes, "Half 
subtilized to chyme the liquid food readiest obeys the assimilating 
powers." Egg-white is then listed as a liquid food and the proper 
conclusion thus drawn. This notion of the easy assimilation of 
liquid foods is often mentioned by writers on dietary topics in their 
discussion of egg-white, and it is taken for granted that such a 
substance offers little resistance to the digestive juices. How far 
astray such an assumption may lead one has already been shown. 

In the larger and more recent text-books on dietetics the use 
of raw eggs is generally recommended. Thompson, whose book 
Practical Dietetics is widely used and much quoted, says on this 
topic: 

'^Yhole raw eggs are very popular in dietetics at present and are 
often prescribed when a nutritious, highly concentrated food is 
desired, as in cases of tuberculosis, some forms of anemia, and 
various wasting diseases; sometimes from eight to ten or twelve 
are given daily if they can be digested." 

Egg albumen is said to be well absorbed and many recipes are 
given for preparing albumen water in a palatable form. It is 
stated, without naming Beaumont, that "a raw egg is ordinarily 
digested in the stomach in one and a half hours, but a baked egg 
requires from three to four hours." 

In Diet in Health and Disease, by Friedenwald and Ruhrah 
(1913), raw eggs are still more strongly recommended. These 
authors state: 

"In various diseases accompanied by loss of flesh and strength, 
raw eggs in large numbers are prescribed, as many as twenty-four 
eggs being given in twenty-four hours. Egg albumen is best 
absorbed when eaten raw. Eggs beaten up in milk are .very useful 
for the diet of the aged when there are diminished powers of diges- 
tion. Raw eggs sometimes disagree but this is more often due 
to faulty preparation than to any real egg idiocyncrasy. In 
tuberculosis raw eggs are of the greatest value; six to twenty-four 
whites may be given daily." 



10 bateman: use of raw eggs in practical dietetics 

These writers — Thompson, Friedenwald and Ruhrah, Pattee, 
Winthrop (1S99) and others — advise raw eggs as part of the diet 
in the treatment of many diseases, such as typhoid, diphtheria, 
gastric ulcer, tuberculosis, appendicitis, gastritis, chronic indigestion, 
etc. We read that "In fevers albumen water helps to supply 
wasted tissue albumin;" that "Raw eggs in consumption are full 
of nutrition and very assimilable;" that "Albumen water is utilized 
by infants, being found very useful in disorders in which some 
nutritious and easily assimilated food is needed." It is more sur- 
prising to find raw egg-white apparently advised in diarrhea and 
contra-indicated in constipation; to find raw eggs and albumen 
water prescribed in dysentery, in chronic cases of which "egg 
albumen and beef juice form the main part of the diet." Again, 
it is often stated that raw egg-white can be retained or "kept on 
the stomach" when nothing else can. This is not really true, since 
it leaves the stomach rapidly, but in a sense contrary to that meant! 

In the treatment of typhoid most writers are agreed that indi- 
gestible food should not be fed and that "those causing the least 
intestinal debris" are the best; yet they all unite in advising raw 
egg-white in the diet. In the current therapy of gastric ulcer 
albumen water is frequently used, with the object of taking up the 
excessive acid. Insofar as it calls forth no more gastric secretion 
its use may be beneficial, but considering the speed with which it 
escapes through the pylorus its efficiency in removing acid already 
present is problematical. One writer says: "The egg-albumen 
should be prepared in such a manner as to require the least possible 
expenditure of force in digestion." Cannon (1904) has shown that 
the intestine expends more motor activity upon the absorption of 
the carbohydrates than upon that of the fats or proteins. Raw 
egg-white, however, acts like a carbohydrate in this respect. 
Another author states that native egg-white is especially valuable 
for those with a "weak digestion." All the evidence gathered in 
this paper tends to show that the substance in question requires 
an exceptionally "strong digestion" if it is to be utilized. 

The most whole-hearted advocate of raw eggs appears to be Dr. 
Ely (1903), who, in "The Fable of the Egg," shows himself a bold 
practitioner of his own ideas. Again, Beaumont is quoted with 
nothing to show that anything has been added to the subject in the 
eighty years since his observations. The number of eggs advised 
and administered may seem "fabulous," as the author admits. 
One patient ate 3006 raw eggs in a year while another partook of 
5475 in the same time, the latter being "an exemplary subject as 
to eggs." It is further stated: 

"Some moral force is necessary on the part of patient, nurse, 
and doctor to overcome a repugnance to the treatment. It is to 
be understood that in every instance they [eggs] have been used 
for their supporting and restorative influence. Although some 



bateman: use of raw eggs IX practical dietetics 11 

patients have died while taking eggs I can think of no case in 
which death was due to their liberal use. If you give eggs to your 
patients do not be chicken-hearted in their employment. Do not 
fear the production of albuminuria from the ingestion of a large 
amount of egg albumen. Notwithstanding all possible efforts, 
nausea and vomiting and diarrhea may often be produced and the 
physician may be thwarted in his object. He will then try the 
whites of eggs alone. I have given the whites of forty-eight eggs 
daily for many days to a patient in the critical stages of typhoid 
fever. Please remember that I am not advocating a fad, specific, 
or 'cure-all.' I would urge that in some chronic cases of exhausted 
nerve centers, and in those acute, critical cases that tax resources 
for maintaining life, they [doctors] should throw away their tonics 
and possibly stimulants and should gradually lead the stomachs 
of their patients up to the egg-an-hour practice." 

Enough has been quoted, perhaps, to show the reasons hitherto 
underlying the advocacy of raw eggs. The results of the present 
study show these reasons to be not well supported and indicate 
that the use of raw egg-white is decidedly inadvisable. A sub- 
stance which fails to stimulate a flow of gastric juice and is anti- 
peptic, which hurries from the stomach, calls forth no flow of bile, 
and strongly resists the action of trypsin, which is poorly utilized 
and may cause diarrhea, has evidently little to recommend it as a 
foodstuff of preference for the sound person, let alone for the 
invalid. And when the native protein needs only to be coagulated 
at 70° in order to obviate almost all the effects mentioned, there 
appears still less reason for using it uncooked. Other considera- 
tions strongly support this conclusion. For instance, Stokvis 
(1864) declared that raw egg-white eaten in quantity is absorbed 
undigested and excreted in the urine, doing thereby some damage 
to the renal epithelium. For a number of years this work was 
disputed by some and confirmed by others. Ascoli (1902) clarified 
the situation somewhat by stating that the alimentary albuminuria 
is not generally manifested by sound persons but usually is by the 
sick. Besides his own observations he cites other investigators 
who found that small kidney lesions were caused in this way. The 
amounts of egg used by Ascoli were not unduly large. The work 
of Hamburger, Oppenheimer, and Oertel on this topic has already 
been mentioned. It should be stated that the subject is still a 
debatable one. 

It is true that fairly large amounts of raw egg-white need to be 
ingested for the abnormal digestive effects to be made manifest; 
but even if small quantities are used, certain disadvantages may 
follow. The indigestible protein may reach the large intestine 
and there become a good pabulum for the putrefactive bacteria. 
Or mixed with other foods it may retard the digestion and lower 
the utilization of other proteins. Again, it seems more than a 



12 bateman: use of raw eggs in practical dietetics 

coincidence that of all the common proteins egg-white is the most 
indigestible and at the same time the most common cause of ana- 
phylaxis. According to the latest views on this subject, as stated 
by Wells (1914), anaphylactic intoxication is caused by the entrance 
into the blood of intact, foreign protein molecules. If this be so, it 
would appear that egg-white is a substance peculiarly apt to be 
the agent in allergy. It leaves the stomach practically unchanged, 
so that in the intestine it may be absorbed still intact or only 
slightly altered. The strong antitryptic action it possesses leads 
to the same danger. Lately, Van Alstyne (1913) has shown that 
egg-albumen can enter into the circulation unaltered and is excreted 
in the urine. In order to cause anaphylaxis it appears unnecessary 
that large amounts should enter the blood, for Wells (1914) has 
shown that in guinea-pigs sensitivity has been produced with one 
twenty-millionth of a gram (0.00000005 gm.) of crystallized oval- 
bumin and fatal results are obtained after sensitization with one 
millionth of a gram (0.000001 gm.). In fact, small amounts are 
frequently more effective than large. It may be argued that 
cleavage products of any protein may be absorbed in small amount. 
This is true; but Wells has found that the protein molecule loses 
its anaphylactic properties as soon as it is altered to any extent. 
He was not able to get reactions from the proteoses of egg-albumen. 
Ten Broeck (1914) found that racemized egg-white had no ana- 
phylactic effect either toward itself or toward native egg-albumen. 
The simpler the protein disintegration products become the less 
toxic is their action. The thorough gastric proteolysis undergone 
by practically all proteins except raw egg-white is a potent factor 
in preventing allergy. It is well established, however, that even 
cooked egg-white cannot be used by those sensitized. This does 
not weaken the case against raw egg, for, as already stated, the 
coagulated egg-white leaves the stomach little less rapidly than 
the uncooked. In the texts and manuals on dietetics quoted 
above the advice to use raw or even cooked eggs is frequently 
safeguarded by the caution that certain people are peculiarly 
susceptible to this foodstuff, and it would appear from the cases 
cited in professional journals that such sensitiveness is not uncom- 
mon. Schloss (1913) reported an interesting case in which the feed- 
ing of raw egg-white to a child ten days old caused it to react for 
years to either cooked or uncooked egg-albumen. The sensitizing 
substance appeared to be ovomucoid while ovalbumin seemed to 
be inactive. 

W r ith the improved technic for rectal feeding effected by the 
drip method there has come an increased interest in this kind of 
alimentation. Since the foods used must be liquid it is natural 
that raw egg-white should suggest itself for the protein require- 
ments. As early as 1S69, Voit and Bauer, however, concluded that 
this foodstuff was practically worthless for the purposes, a con- 



bateman: use of raw eggs in practical dietetics 13 

elusion also reached by Eichorst. Previously it had been stated 
that salt aided in the absorption of the egg-white, but Eichorst 
doubted this and stated that the salt caused diarrhea. Czerny 
and Latschenberger (1874) and Ewald (1887) also found the salt 
to be of no value. More recent studies of rectal alimentation 
tend to show that the amount of protein which can be utilized 
in this way is unimportant compared to the requirements of the 
body, a conclusion supported by the work of Adler (1915). 
Furthermore, it is considered doubtful if unaltered proteins can 
be absorbed from the colon (PfeifTer, 1906). If this is so, native 
egg-white must be considered an especially poor substance for 
nutrient enemas in view of its pronounced antitryptic properties. 
It must not be assumed from the foregoing discussion that 
native egg-white is considered a toxic or otherwise dangerous 
substance. But the evidence regarding its behavior in the ali- 
mentary canal is taken to show that no advantage accrues to the 
body by using it raw rather than cooked. Furthermore, when 
the diet of those seriously ill is considered it may fairly be asked 
in the light of scientific evidence if the current extensive use of 
raw eggs is not illogical and inadvisable? 

REFERENCES. 

Abderhalden and Pettibone: Ueber den Einfluss des physikalischen Zustandes 
von Proteinen auf die Raschheit ihres Abbaues durch Fermente, Ztschr. f. physiol. 
Chem., 1912, lxxxi, 458. 

Adler: Value of Rectal Feeding, Am. Jour. Med. Sc, 1915, cl, 562. 

Ascoli: Ueber den Mechanismus der Albuminuric durch Eiereiweiss, Miinchen. 
med. Wchnschr., 1902, xlix, 398. 

Ascoli and Vigano: Zur Kenntniss der Resorption der Eiweisskorper, Ztschr. f. 
physiol. Chem., 1903, xxxix, 283. 

Bateman: The Digestibility and Utilization of Egg Proteins, Jour. Biol. Chem., 
1916, xxvi, 263. 

Bayliss: The Nature of Enzyme Action, London, 1908. 

Beaumont: The Physiology of Digestion, Plattsburg, 1833. 

Bizarro: On the Influence of Preliminary Heating upon Peptic and Tryptic 
Proteolysis, Jour. Physiol., 1913, xlvi, 267. 

Bruno and Klodnizki: (Quoted from: Babkin, Die aussere Secretion der Verdau- 
ungsdriisen, 1914.) 

Cannon : The Passage of Different Foodstuffs from the Stomach and Through the 
Small Intestine, Am. Jour. Physiol., 1905, xii, 387. 

Cathcart and Green: The Rate of Protein Metabolism, Biochem. Jour., 1913, vii, 1. 

Chambers: A Manual of Diet, Philadelphia, 1875. 

Chittenden, Joslin, and Meara: On the Ferments Contained in the Juice of the 
Pineapple, Tr. Conn. Acad. Arts. Sc, 1892, viii, 281. 

Chittenden: Proteolytic Action of Bromelin, Jour. Physiol., 1894, xv, 249. 

Cohnheim: Enzymes, New York, 1912. 

Cramer: On the Assimilation of Protein Introduced Parenterally, Jour. Physiol., 
190S, xxxvii, 146. 

Czerny and Latschenberger: Physiologische Untersuchungen iiber die Verdauung und 
Resorption im Dickdarm des Menschen, Arch. path. Anat. u. Physiol., 1874, lix, 161. 

Delezenne and Pozerski: Action empechante de " l'ovalbumine crue" sur la diges- 
tion tryptique de "l'ovalbumin coagulee," Comp. Rend. Soc. biol., 1903, lv, 935. 

Eichorst: Ueber die Resorption der Albuminate im Dickdarm, Arch. ges. Physiol., 
1871, iv, 570. 

Ely: The Fable of the Egg, New York Med. Jour., 1903, lxxviii, 92S. 



14 bateman: use of raw eggs in practical dietetics 

Ewald: Ueber die Ernahrung mit Pepton- und Eierklystieren, Ztschr. f. klin. 
Med., 1887, xii, 407.. 

Falta: Studieren tiber den Eiweissstoffwechsel, Deutsch. Arch. f. klin. Med., 
1906, lxxxvi, 517. 

Falta and Noeggerath: Fiitterungsversuche mit Kiinstlicher Nahrung, Beitr. z. 
chem. Physiol., 1905, vii, 314. 

Frank: The Digestibility of White of Egg as Influenced by the Temperature at 
Which it is Coagulated, Jour. Biol. Chem., 1911, ix, 463. 

Frank and Schittenhelm : Ueber die Brauchbarkeit tief abgebauter Eiweiss- 
praparate ftir die Erniihrung, Therap. Monatsh., 1912, xxvi, 112. 

Friedenwald and Ruhrah: Diet in Health and Disease, Philadelphia, 1913. 

Gompel and Henri: Etude du ralentissement que produit l'albumine d'oeuf crue 
sur la digestion tryptique de l'albumine coagulee, Comp. Rend. Soc. biol., 1905, 
lviii, 457. 

Hamburger: Zur Frage der Immunisierung gegen Eiweiss, Wien. klin. Wchnschr., 
1902, xv, 1188. 

Hedin: An Antitryptic Effect of Charcoal, Biochem. Jour., 1906, i, 484. 

Hedin: Ueber Verschiedenartige Hemmung der Tryptischen Verdauung, Ztschr. 
f. physiol. Chem., 1907, Hi, 412. 

Jonescu : Ueber eine eigenartige Verdauung des Hiihner- und Serum-eiweiss durch 
Papain, Biochem. Ztschr., 1907, ii, 177. 

Knapp: Experimenteller Beitrage zur Ernahrung von Ratten mit kiinstlicher 
Nahrung, Ztschr. f. exper. Path. u. Therap., 1908, v, 147. 

Langworthy: Eggs and their Uses as Food, United States Department of Agricul- 
ture, Farmers' Bull. 128, 1906. 

LeClerc and Cook: Metabolism Experiments with Organic and Inorganic 
Phosphorus, Jour. Biol. Chem., 1906, ii, 203. 

London and Sulima: Zum Chemisrnus der Verdauung im tierischen Korper, 
Ztschr. f. Physiol. Chem., 1905, xlvi, 209. 

Long and Johnson: Activity and Stability of Certain Ferments, Jour. Am. 
Chem. Soc, 1913, xxxv, 1188. 

Maignon: Role des graisses dans l'utilization de l'albumine alimentaire, Comp. 
Rend. Soc. biol., 1912, lxxii, 1054. 

Maxwell: The Relation of Salivary to Gastric Digestion, Biochem. Jour., 1915, 
ix, 323. 

Mendel and Lewis: Rate of Elimination of Nitrogen as Influenced by Diet 
Factors, Jour. Biol. Chem., 1913, xvi, 55. 

Mendel and Rockwood: On the Absorption and Utilization of Proteins, Am. 
Jour. Physiol., 1905, xii, 336. 

Mendel and Rose: Experimental Studies on Creatine and' Creatinine, Jour. 
Biol. Chem., 1911, x, 213. 

Oertel: Ueber Ernahrung mit Huhnereiern, Miinchen., 1883. 

Okada: On the Secretion of Bile, Jour. Physiol., 1915, xlix, 458. 

Oppenheimer: Ueber das Schicksal der mit Umgehung des Darmskanals einge- 
fuhrten Eiweissstoffe im Tierkorper, Beitr. z. chem. Physiol., 1904, iv, 263. 

Osborne and Campbell: The Protein Constituents of Egg-white, Jour. Am. Chem. 
Soc, 1900, xxii, 422. 

Osborne and Mendel: Feeding Experiments with Isolated Food-Substances, 
Carnegie Institution of Washington, Publication No. 156, 1911. 

Pattee: Practical Dietetics with Reference to Diet in Disease, New York, 1910. 

Pawlow: The Work of the Digestive Glands, London, 1902. 

Pfeiffer: Ueber Ausnutzung von Eiweissklystieren, Ztschr. f. exper. Path., 1906, 
cxi, 89. 

Rohmann : Ueber die Ernahrung von Mausen mit einer aus einfachen Nahrungs- 
stoffen zusammengesetzen Nahrung, Biochem. Ztschr., 1914, lxiv, 30. 

Rubner: Ueber die Ausnutzung einiger Nahrungsmittel in Darmkanals des 
Menschen, Soc Biol., 1879, xv, 115. 

Sachs: Ueber die Verdauung von rohem Hiihnereiweiss durch Papain, Ztschr. f- 
physiol. Chem., 1907, li, 488. 

Schloss: A Case of Allergy to Common Foods, Am. Jour. Dis. Child., 1912, hi, 34. 

Steinitz: Ueber das Verhalten phosphorhaltiger Eiweisskorper im Stoffwechsel, 
Arch. ges. Physiol., 1898, lxxii, 75. 

Stokvis: Huhner-eiweiss und Serum-eiweiss und ihr Verhalten zum thierischen 
Organismus, Zentralbl. f. med. Wiss., 1864, ii, 596. 



bateman: use of raw eggs in practical dietetics 15 

Talarico: De l'influence de la cuisson sur la digestibilite tryptique de l'albumine 
d'oeuf, Comp. Rend. Soc. Biol., 1910, Ixviii, 662. 

Ten Broeck: The Non-antigenic Properties of Racemized Egg Albumin, Jour. 
Biol. Chem., 1914, xvii, 369. 

Thompson: Practical Dietetics, New York, 1902. 

Tsuchiya: Ueber das Auftreten des gelosten Eiweisses in den Faces Erwachsener, 
Ztschr. f. exper. Path. u. Therap., 1908, v, 455. 

Van Alstyne: The Absorption of Proteins without Digestion, Arch. Int. Med., 
1913, xii, 372. 

Vernon: Proteids and Trypsin Destruction, Jour. Physiol., 1904, xxxi, 346. 

Voit and Bauer: Ueber die Aufsaugung im Dick und Dunndarme, Ztschr. f. 
Biol., 1869, v, 536. 

Vogt: Der Zeitliche Ablauf der Eiweisszersetzung bei Verschiedener Nahrung, 
Beitr. z. chem. Physiol, u. Path., 1906, viii, 409. 

Von Knieriem: Ueber die Verwerthung der Cellulose im Thierischen Organismus, 
Ztschr. f. Biol., 1885, xxi, 67. 

Wells: Chemical Pathology, Philadelphia, 1914. 

Winthrop: Diet in Illness and Convalescence, New York, 1899. 

Wolf: Die Ausschiedungzeit von Stickstoff, Schwefel, und Kohlenstoff nach 
Aufnahme von Eiweisssubstanzen und ihren Spaltungsprodukten, Biochem. Ztschr., 
1912, xl, 234. 



